A simple sentence has just one clause. A complex sentence has one main clause and one or more subordinate clauses. A compound sentence has more than one main clause 
The following are some rules of Transforming Sentences.
RULE 1
RULE 1
-          Put ‘although / though’ in the beginning of the sentence.
-          Remove ‘but / yet / still’ from the original sentence.
Example 1:
-          Tashi is rich but he doesn’t help others.
-          Although Tashi is rich, he doesn’t help others.
RULE 2
-          Replace ‘so…that’ with ‘too…to’.
[Note: too + adj/adv + to + verb]
-          Remove negative form.
Example 1:
-          He is so sick that he cannot walk (to hospital).
-          He is too sick to walk (to hospital).
Example 2:
-          Sonam is so wise that she cannot fail her exam.
-          Sonam is too wise to fail her exam.
RULE 3
-          Replace ‘too…to’ with ‘so …that’
-          Add negative form to the second clause
[Note: so + adj/adv + that + pronoun + not]
Example 1:
-          The tree is too high for me to climb.
-          The tree is so high that I cannot climb.
Example 2:
-          He is too proud to beg for forgiveness.
-          He is so proud that he cannot beg for forgiveness.
RULE 4
-          Begin with ‘No sooner’  + [had + Past participle]  + than + second clause
-          Begin with ‘No sooner’  + [did + Present tense]  + than + second clause
Example 1:
-          As soon as teacher came in, the students got up.
-          No sooner did teacher come in than the students got up.
Example 2:
-          As soon as police saw, the thieves ran away.
-          No sooner did police see than the thieves ran away.
RULE 5
-          Begin with ‘Hardly’ + [had + Past participle] + when + second clause
-          Begin with ‘Hardly’ + [did + Present tense] + when + second clause
Example 1:
-          As soon as he saw me, he fled.
-          Hardly did he see me when he fled.
Example 2:
-          No sooner had I posted the letter that I got a call.
-          Hardly had I posted the letter when I got a call.
RULE 6
-          Begin with ‘In spite of’ + ing Verb + second clause.
-          Remove: but / yet / still
Example 1:
-          Karma was an ordinary singer but he fought his way to success.
-          In spite of being an ordinary singer, Karma fought his way to success.
Example 2:
-          It was cold yet we marched on.
-          In spite of being cold, we marched on.
RULE 7
-          Begin with ‘Despite’ + noun +ing Verb + second clause
-          Remove: but / yet / still
Example:
-          Even though the car was old, (still) it went very fast.
-          Despite the car being old, it went very fast.
RULE 8
-          Begin with ‘Having’ + past participle
Example 1:
-          After she completed her work, she went home happily.
-          Having completed her work, she went home happily.
Example 2:
-          After he wrote the letter, he burnt it.
-          Having written the letter, he burnt it.
RULE 9
-          Replace ‘…and…’ with ‘Not only…but also…’
Example:
-          She likes music and reading.
-          Not only does she like music but also reading.
RULE 10
-          Begin with ‘Unless’
[Note: change ‘If (negative)’ to ‘Unless”]
Example 1
-          If you don’t go immediately, you will not meet him.
-          Unless you go immediately, you will not meet him.
Example 2:                     
-          If Sonam does not study, she will fail.
-          Unless Sonam studies, she will fail.
RULE 11
-          Begin with ‘On’ + ing Verb + second clause.
Example:
-          When he entered the room, he heard a great noise.
-          On entering the room, he heard a great noise.
RULE 12
-          Using ‘neither…(nor)’
[Remove: not]
Example:
-          He did not qualify for job and RCSC.
-          He neither qualified for job nor RCSC.
Example:
-          Both her parents don’t like music.
-          Neither of her parents like music.
RULE 13
-          Using ‘either…or’
Example:
-          Nima will come or she will write a letter.
-          Nima will either come or she will write a letter.
RULE 14
-          Use ‘enough to’ to join two sentences.
Example:
-          He is tall. He can play basketball.
-          He is tall enough to play basketball.
*Remove subject from the second clause.
RULE 15
-          Begin with ‘Besides’ + ing Verb + second clause
-          Remove: but / yet / still
Example
-          He not only robbed the bank, but also killed the manager.
-          Besides robbing the bank, he also killed the manager.
RULE 16
-          Use ‘both…and…’ to join the sentences.
Example:
-          He is very foolish. His wife is also as foolish as him.
-          Both he and his wife are foolish.
RULE 17
-          Begin with ‘Not withstanding’ + pronoun + noun
-          Remove: but / yet / still
*Not withstanding = Even though
Example 1:
-          He worked hard but he did not succeed.
-          Not withstanding his hard work, he did not succeed.
Example 2:
-          My mother is very old but she works hard.
-          Not withstanding her old age, she works hard.
RULE 18
-          Using ‘such…that’
-          [Note: such + article + adj + that + second clause]
Example:
-          He was a gentleman. Everybody respected him.
-          He was such a gentleman that everybody respected him.
RULE 19
-          Using ‘…as well as…’ to join sentences.
Example:
-          She is bright. She is clever.
-          She is bright as well as clever.
RULE 20
-          Using ‘as if’ or ‘as though’
-          [Note: ‘as if’ + second clause (past tense)]
-          [Note: ‘as though’ + second clause (past tense)]
-          Remove: ‘one might think that’, ‘one might suppose that’, ‘it seemed that’, ‘like’, ‘pretended to be’..etc
Example:
-          Sonam was sleeping. He pretended to be sick.
-          Sonam was sleeping as if he was sick.
RULE 21
-          Using ‘Incase’ + present + tense (Future)
[Note: Don’t use modal verb after ‘in case’]
Example:
-          Dawa may call. I don’t want to go out today.
-          I don’t want to go out today incase Dawa calls.
-          Incase Dawa calls; I don’t want to go out today.
RULE 22
-          Begin with ‘Even though’ of ‘Even if’
-          Remove : but / yet / still
Example:
-          I will never sell another record but I will continue to sing.
-          Even though I will never sell another record, I will continue to sing.
 RULE 23
-          Begin with ‘Scarcely’ + [had  + past participle] + when + second clause
-          Begin with ‘Scarcely’ + [did  + past tense] + when + second clause
Example:
-          As soon as she saw her mother, she began to cry.
-          Scarcely had she seen her mother when she began to cry.
RULE 24
-          Begin with ‘As soon as’ + noun + verb
-          Replace: ‘Hardly / Scarcely / No sooner’ with ‘As soon as’
-          Remove: than / when
Example
-          Hardly did we hear the news when we rushed out.
-          As soon as we heard the news, we rushed out.
RULE 25
-          Replacing ‘still’ with ‘nevertheless’
Example:
-          Tandin was tired still she continued to work.
-          Tandin was tired nevertheless she continued to work.
RULE 26
-          Interchange of Assertive sentences to Exclamatory sentence.
-          *Assertive = Starting out as opinion
Example 1:
-          It was stupid of me to forget you. (AS)
-          How stupid of me to forget you! (ES)
Example 2:
-          What a beautiful day! (ES)
-          It is a beautiful day. (AS)
-          How beautiful the day is! (ES)
EXERCISE 1
Rewrite each sentence suing the instruction given in brackets.
1.      A soon as I arrived in Thimphu, I was to go straight to the hotel. (Begin: on)
·         On Arriving in Thimphu, I was to go straight to the hotel.
2.      Pema has taken his friend’s book and spoiled it. (Begin: Not only)
·         Not only has Pema taken his friend’s book but also spoiled it.
3.      After they had rested, the men continued their journey. (Use: having)
·         Having rested, the men continued their journey.
4.      Dorji was not rich. He was not handsome. (Use: neither…nor)
·         Dorji was neither rich not handsome.
5.      He is intelligent. He can learn it. (Use: enough to)
·         He is intelligent enough to learn it.
6.      He is too honest to accept a bribe. (Use: so …that)
·         He is so honest that he cannot accept a bribe.
7.       He is very old man. He cannot run like you. (Use: such… that)
·         He is such an old man that he cannot run like you.
8.       He is so sleepy that he could not stay awake. (Use: too…to)
·         He is too sleepy to stay awake.
9.       As soon as he got the letter, he left for Thimphu. (Begin: No sooner )
·         No sooner did he get the letter, than he left for Thimphu.
10.  Although it was a cloudy day, the temperature is 40oC. (Use: In spite of)
·         In spite of being a cloudy day, the temperature was 40oC.
EXERCISE 2
Instruction: Use any form of the word given in the brackets.
1.      Dema seldom earns more than Nu. 15,000/- in a month. (income)
·         Dema’s monthly income doesn’t exceed Nu. 15,000/-
2.      My uncle appears from time to time on television. (occasionally)
·         My uncle appears on television occasionally.
3.       Kuenzang knows nothing of the customs of his people. (ignorant)
·         Kuenzang is ignorant of the customs of his people.
4.       The Indian museum has borrowed a relic for six months. (loan)
·         A relic is on loan to the Indian museum for six months.
5.      What do you think about the situation in Nepal? (opinion)
·         What is your opinion about the situation in Nepal?
6.       Rinzin inherited a lot of money after his father’s death. (inheritance)
·         Rinzin has got a lot of money as inheritance after his father’s death
7.       Deki did not mean to hurt the dog. (intention)
·         Deki’s intention was not to hurt the dog.
8.       Few good doctors are to be found in our village. (dearth)
·         There is no dearth of good doctors in our village
9.      During diwali lights are set up all over our home. (illuminated)
·         During diwali lights are illuminated all over our house.
10.   Fish is sold according to weight. (depends)
·         Selling of fish depends on its weight.
·         Sale of fish depends on its weight.
EXERCISE 3
Instruction: Use any form of the word given in the brackets.
1.      This matter must be investigated very carefully. (require)
·         This matter requires a careful investigation.
2.      The museum is open to tourists beyond this point. (permit)
·         The museum is permitted to tourists beyond this point.
3.      Choden has been put in charge of the factory. (management)
·         Choden has been put in management of the factory.
4.      The two smugglers were arrested by the police. (custody)
·         The two smugglers are under custody of the police.
5.      I consider Singapore a friendlier city than London. (opinion)
·         In my opinion Singapore is a friendlier city that London.
6.      Sangay got back his property ten years later.  (restored)
·         Sangay’s property was restored ten years later.
7.      Both Lhamo and Lhendup look like their father. (resemblance)
·         Both Lhamo and Lhendup have a resemblance to their father.
8.       I wonder if it was possible to stay here. (thought)
·         I thought if it was possible to stay here.
9.      Karma is not very keen on western food. (care)
·         Karma does not care about western food.
10.  Jampel was given more than he could manage. (cope)
·         Jampel was given more than he could cope.