Is x^2*y^4 divisible by 9?
1. x is an integer divisible by 3
2. xy is an integer divisible by 9
I'd say E
(1) we don't know if y is an integer, so INSUFF
(2) again, we don't whether x and y are integers (consider x=2 and y=4.5). INSUFF
(1)+(2). By the same token, it could be that x=3 and y=3 (the answer is YES), or x=6 and y=3/2 (the answer is NO). INSUFF