2个GWD的题求解，谢！

Q25:

If n is an integer greater than 6, which of the following must be divisible by 3? 

A.          n (n+1) (n-4)

B.          n (n+2) (n-1)

C.          n (n+3) (n-5)

D.          n (n+4) (n-2)

E.          n (n+5) (n-6)

Q17:

Meg and Bob are among the 5 participants in a cycling race.  If each participant finishes the race and no two participants finish at the same time, in how many different possible orders can the participants finish the race so that Meg finishes ahead of Bob?