Did you try looking . . . . . . . . the door or . . . . . . . . cupboard?

A. under, behind

B. behind, in

C. in, over

D. at, in

Answer: Option B

Solution(By Examveda Team)

In the first blank, 'behind' will be used because it means 'at or to the far side of (something), typically so as to be hidden by it'.
In the second blank, 'in' will be used because it is used when something is within, i.e. one thing contains another.