I made an assumption here that that the left hand side was in its prime factorized format. Was I wrong to assume because it was not explicitly stated? I chose B and then saw the answer was D. That felt like such a cheap shot! 
I think you missed the x= 45 and y= 1 case as the common case after PF is 9^2 and 5^3 seems like the go to answer.
As 10,125 = 3^4 and 5^3
we can either do (3^2)^2 \times 5^3 or (3\times3\times5)^2 \times 5
Yes I did! But I was just so flustered after being tricked. “Manhattan, you snake!” was my reaction. I know these problems lie on the difficult side of the spectrum but can I expect this level of slickness on the real test?