What is the greatest positive integer x such that 3^x is a factor of 9^7?  Choose one:
A) 5
B) 14
C) 10
D) 20
E) 30

Rationale: what is the greatest positive integer x such that 3 ^ x is a factor of 9 ^ 7 ? 9 ^ 7 = ( 3 ^ 2 ) ^ 7 = 3 ^ 14 b . 14
Answer: B