GWD27-32

bth

(1) put y = 1, then x = cube root (5000)

put y = 2, then x = cube root(5000/16) and so on... --> Insuff

(2) put x = 1, y = 5000^1/4
put x = -1, y = - (5000^1/4)

put x = 3, y = (5000/8)^1/4 and so on... --> Insuff

1 & 2 - Together x and y can only be integers and y only positive - Suff

Hence, C