请教prep里的一道应该是关于数论的题～～

haiya

for every positive even integer n， the function h(n) is defined to be the product of all the even integer from 2 to n, inclusive. if p is the smallest prime factor of h100)+1, then p is between:
a. 2 to 10   b.10 to 20   c. 20 to 30   d.30 to 40   e.greater than 40

这道题应该怎么做呀，我连点思路都没有，后天就要考了～～～