If k is a non-negative integer and 21^k is a divisor of 435,961 then 7^k - k^7 =	Choose the correct choice from the following choices.
A) 0	B) 1	C) 42	D) 118	E) 242

Rationale: "4 + 3 + 5 + 9 + 6 + 1 = 28 , so this number is not divisible by 3 and thus not divisible by 21 . therefore , k = 0 7 ^ k - k ^ 7 = 1 - 0 = 1 the answer is b ."
Answer: B