A set of numbers has the property that for any number t in the set, t + 2 is in the set. If -1 is in the set, which of the following must also be in the set?
I. -3 II. 1 III. 5
A. I only B. II only C. I and II only D. II and III only E. I, II, and III 怎么我感觉答案是E,但是GWD的答案是D,求救啊!!!