Cambridge Grammar of English Hardback with cd-rom a comprehensive Guide

Prepositions and particles with wh-interrogatives 

292e

Wh

-words and wh-phrases can be the complement of a preposition, in which case the

preposition and its complement typically occur together in more formal styles:

To whom did the last item belong?

(wh-word)

For what purpose could it be used?

(wh-phrase)

In informal styles, especially in spoken language, the preposition may be stranded

(separated from its complement, 

Û

257

) and placed at the end of the clause:

[writing a cheque]

Who do I make it out to?

Where do you get them from?

In the case of reduced questions, the preposition and its complement normally occur

together:

A: She was quite upset.

B: For what reason?

(What reason for?)

A marriage of convenience, if ever there was one. But 

for what motive?

(But what motive for?)

With phrasal verbs, which are combinations of verbs and particles (

Û

235c

), the particles

stay attached to the verb, rather than to the wh-word:

What did they get up to?

(What mischief/misbehaviour were they involved in?)

(Up to what did they get?)

Which dictionary shall I look it up in? 

(or, in formal style: In which dictionary shall I look it up?)

(Up in which dictionary shall I look it?)