Suppose S is a recursively defined set, defined by the number 1 is in S if n is in S, then so is 3n+2 - if n is in S, then so is 5n-1 if n is in S, then so is n+7 Suppose you want to prove using structural induction that all members of S have a certain property. What do you have to prove in the base step? That the numbers 5,4 and 8 have the property. That the number 1 has the property, and the numbers 5, 4 and 8. O That the numbers 5, 4 and 8 are in the set S. That the number 1 has this property.