Let Z17 be the ring of integers modulo 17, and let Z17* be the group of units of Z17 under multiplication. Which of the following are generators of Z17*?
I.5
II.8
III.16
(A) None (B) I only (C) II only (D) III only (E) I, II, and III
官方给的答案是B 不太懂了,不应该和17互素的数都是生成元么