Bunuel wrote:

x and y are two positive integers. D is the greatest common divisor of x and y. Is D > 20?

(1) x is a multiple of 4

(2) y is a multiple of 20

Stat 1: Given x is a multiple of 4 and x can be 20,24,28...etc...but we don't have information about y...Insufficient.

Stat 2: Y can be 20,40,80...but we don't have information about x...Insufficient.

Stat 1+2 : Now we can take x as 24 and y as 40 then GCD is 8. now if x is 8 and y is 20 then we GCD is 4...we can get different GCDs based on numbers we assume...no unique result..Insufficient.

IMO option E.