We say that prepositions govern nouns and pronouns, and that nouns and pronouns which come after prepositions are in the objective case.

Sometimes prepositions follow the nouns or pronouns which they govern. This is common in Spoken English.

We say: To whom shall I give this book? or Whom shall I give this book to?

Note. It would not be correct to say Who shall I give this book to? because after a preposition the pronoun who must be in the objective case, whom.

Examples.

Which shop did you buy this card at?

I have seen the film that you spoke of.

The place which I went to is quite near Anuradhapura.

The tunnel which the train went through is nearly a mile long.

What is the dog running after?

Which part of Sri Lanka do you come from?

If you look carefully at these sentences you will see that they are of two kinds, one interrogative, and the other kind containing relative pronouns. Often the relative pronoun is left out.

The place I went to is quite near Anuradhapura.

I have seen the film you spoke of.