option D is NOT possible.
Because in that case Y= 9 and X=0
So the two digit number becomes 09 which is NOT a two digit number but a ONE digit number.
Hence option D is NOT possible.

Lets see if the other options CAN BE or CANNOT BE.
A. X + Y = 9 -> X=8 and Y=1 so two digit number is 81 CAN BE.
B. (X)(Y) = 9 ->X=9 and Y=1 so two digit number is 91 CAN BE.
C. X – Y = 9-> X=9 and Y=0 so two digit number is 90 CAN BE.
D. Y – X = 9-> X=0 and Y=9 so two digit number is 09 CANNOT BE.
E. X/Y=9 -> X=9 and Y=1 so two digit number is 91 CAN BE.

Ans-D

Hope it's clear.
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