A set of numbers has the property that for any number t in the set, 3t + 1 is in the set. If -1 is in the set, which of the following must also be in the set?
I. -3
II. 10
III. 5	Choose the correct choice from the following answers:
A) I only	B) II only	C) I and II only	D) II and III only	E) I, II, and III
The question is which of the followingmustbe in the set, notcouldbe in the set.   If -1 is in the set so must be 3*-1+1=-2, as -2 is in the set so must be 3*-2+2=-4, as -4 is in the set so must be 3*-4+2=10 and so on.   Answer: II only.
<result>B</result>
A set of numbers has the property that for any number t in the set, 3t + 1 is in the set. If -1 is in the set, which of the following must also be in the set?
I. -3
II. 10
III. 5