PREPOSITIONS IN QUESTIONS

1.   We often put a preposition (with, at, for etc.) at the end of a question with Who...? or What...?, especially in spoke English.

Examples:

a.   Who did you go with? (More natural than With whom did you go?)

b.   Who is that letter for?
c.   What are you looking at?
d.   What's she talking about?

2.   We also ask questions with Where ... from? and Where ... to?

a.   Where do you come from? (Or Where are you from?)
b.   Where shall I send the letter to?

3.   In conversation, we often ask short questions with Who/What/Where + preposition.

Examples:

a.   'I'm going camping.' 'Who with?'

b.   'Peter wants to talk to you.' 'What about?'