If x and y are different prime numbers, each greater than 2, which of the following must be true ?()
Ⅰx+y≠91
Ⅱx-y is an even integer.
Ⅲ is not an integer.
A.条件(1)充分,但条件(2)不充分.
B.条件(2)充分,但条件(1)不充分.
C.条件(1)和(2)单独都不充分,但条件(1)和条件(2)联合起来充分.
D.条件(1)充分,条件(2)也充分.
E.条件(1)和条件(2)单独都不充分,条件(1)和条件(2)联合起来也不充分.