What for? = why?

[naif]

English Grammar Tests, Elementary Level

ESL/EFL Test #61 "Chit Chat: In the supermarket", question 9

Employee: It's Thursday of course. What do you want to know .........?

(a) to
(b) at
(c) up
(d) for

English Grammar Tests, Elementary Level

ESL/EFL Test #61 "Chit Chat: In the supermarket", answer 9

Employee: It's Thursday of course. What do you want to know for?

Correct answer: (d) for
_________________________

It's Thursday of course. What do you want to know .........?

naif

[Mister Micawber]

.
What do you want to know for? = Why do you want to know?
What for? = why?
.
_________________
Native English teacher at Mister Micawber's