In formal, usually written English, we tend to put the preposition before the relative pronoun.
eg. It’s David’s book on which the film was based.
In less formal, usually spoken English, we tend to put the preposition at the end of a relative clause.
eg. It’s David’s book that the film was based on.
When transforming informal sentences of this kind to more formal English, we follow these rules:
– if the relative pronoun ‘that’ refers to a person, we change it to ‘who’ or ‘whom’
– if the relative pronoun ‘that’ refers to a thing, we change it to ‘which’
– we move the preposition from the end of the sentence to before the relative pronoun.
eg. She’s the woman who I spoke to yesterday. —> She’s the woman to whom I spoke yesterday.
It’s David’s book that the film was based on. —> It’s David’s book on which the film was based.
None/ Both/ All/ One/ Neither/ Most… Of Which/ Whom
Determiners combine wıth ‘of which’ or ‘of whom’ in non-defining relative clauses. They refer to words or phrases in the previous clause.
eg. This is one of many of his jokes, none of which are particularly funny.
In formal written English we can use
– ‘both of whom’, instead of ‘who both’
eg. He invited two friends from university, both of whom now reside in New York.
– a relative clause with ‘all of which’ instead of a normal clause with ‘all’
eg. She found some jeans, a coat and two sweaters that were suitable and bought them all.
—> She found some jeans, a coat and two sweaters that were suitable, all of which she bought.