The following are simple sentences:

• Simple sentences have only one verb.
• They contain only one main idea.
• Complex sentences have two or more verbs.
• They consist of two or more clauses.
• They contain more than one main idea.

English uses CONJUNCTIONS to join simple sentences  into complex sentences. In the above example I have used the conjunction ‘and’. This is the easiest way to join sentences in English, but other conjunctions you can use are BUT, ALTHOUGH, THEN, AS, SO, WHEN, BECAUSE, THAT.  There are more. (Visit Linda Bryson's page on conjunctions for a more complete list.)
 

Exercise:

Write complex sentences from the following simple sentences.

1)

• Princess Diana died in a car accident in Paris.
• It was very sad.
• Michael agreed.
• The paparazzi were partly to blame.
• The drunk driver was also guilty.

2)

• We read an article on migrants and swearing.
• We had to answer some comprehension questions.
• Many students did not answer the questions in sentences.
• Many students had to do some questions again.
• Several students wrote good answers.

3)

• Michael took his camera to the volleyball.
• Peter took some photos.
• Michael took some photos.
• It was hard to take photos.
• Everybody was moving too fast.
• They didn't take many photos.

4)

• Thanh didn't want to play volleyball.
• She walked around on her own for awhile.
• Ricardo came late.
• He played basketball with Thanh.
• Roberto also played basketball with them

• Some students like studying English on the Internet.
• They enrol in classes.
• Some students take a long time to finish assignments.
• They are very busy.
• The teacher is very busy.
• The teacher wonders if the students are still enrolled.