You can use relative clauses to give essential or extra information about a person, place, or thing.
This makes our writing more fluent and more coherent. We do this by using relative pronouns like “who”, “which” and “that”. For example, ‘He’s the kind of person who is always friendly.’
Air pollution can cause health problems. Air pollution is largely caused by motor vehicles.
We can convert these two simple sentences in to one complex sentences by using the word ‘which’.
Air pollution, which is mostly caused by motor vehicles, can cause health problems.
There is evidence that some people are more likely to smoke. These people have parents and friends who smoke.
We can link both of these sentences together by using the word ‘that’.
There is evidence that people who have parents and friends that smoke are more likely to smoke