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. -3II. 1III. 5
Ionly
IIonly
Iand II only
IIand III only
I,II, and III
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t+2右边的一定成立,左边的不一定
t+2右边的一定成立,左边的不一定
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