Task: Question Answering
Input (English): Question: 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. 5
II. 1
III. -5

 Option A: I only

 Option B: II only

 Option C: I and II only

 Option D: II and III only

 Option E: I, II, and III
Output (English): Option C