There are often prepositions in relative clauses, and the relative pronoun is the object of the preposition. This means that the preposition can sometimes be omitted.
- The preposition is normally placed at the end of the relative clause:
Is that the man (who) you arrived with?
Do you know the girl (that) John is talking to?
- In formal or written English, the preposition is often placed before the relative pronoun, and in this case the pronoun cannot be omitted:
The person with whom he is negotiating is the Chairman of a large company.
It is a society to which many important people belong.
However, this is unusual in spoken English.
- The jungle the elephant lived in was full of strange and unusual animals.
- He was very fond of the mouse that he lived with.
- The tree under which they had their home was the largest and oldest in the jungle.
- In the middle of the jungle was a river that all the animals went to every day.
- It was the stream in which the elephant and the mouse preferred to swim.