Let's reason through the answers...
A) Do you see any sums? Any addition? Me neither... it's not A.
B) Well I see a product of 2 and "some number," but are we dividing by 2? Nope. Not B.
C) I see a quotient (2x) divided by 4, but the "some number" is not being multiplied by four. Not C.
D) Well this is the only one left, so it better be this one! We have a quotient, and we have two times some number (2x). The quotient (the division) is of 2x and four. This is it! It's D.
