求助- math-online FF

if y=/=3 and 3x/y is a prime integer greater than 2, which of the following must be true?

1. x=y

2. y=1

3. x and y are prime integers.

A. none

B.1 only

C. 2 only

D 3 only

E. 1 and 3

answer: A

I think the answer is B.

Thanks in advance!