GWD-1-Q10

Q10:

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

答案是D,   -3不是？？？怎么解释啊？

原来是这样啊

看来思路得改了

多谢这位仁兄了