请教数学data sufficiency 一题

沉睡的巨人

How many different factors does the integer n have?
(1) n=a^4*b^3,where a and b are different positive prime numbers.
(2) The only positve prime numbers that are factors of n are 5 and 7.

(2) 单独为什么不能推出结论？
答案是A，我选D
非常感谢！

cb2713

n可能是负数