If x and y are positive integers, and y=x^2+8, the greatest common divisor of a and b CANNOT be	Choose the correct choice.
A) 9
B) 1
C) 2
D) 4
E) 8

Rationale: if x is 1 , 2 , 4 , or 8 , then gcd of x and y is 1 , 2 , 4 , and 8 respectively . so , by poe the answer must be a . still : if x is a multiple of 9 , then y is 8 greater than a multiple of 9 , so not a multiple of 9 , so both of them can not be divisive by 9 . answer : a .
Answer: A