Which South hand fits the bidding best?  

Solution

South's bid is compulsory. If he bids in a new suit without jumping, he therefore promises 'nothing', say 0-7 points. As a consequence he would jump in a new suit having 8-11 points. Such a jump is not forcing but invitational.
Only no trump bids have the same strength and about the same meaning as on partner's opening bid ('about' because a guard in the opponent's suit is required).
The only forcing bid is a cue bid, here that would be 2♠.

South 1 is far too strong for a 2♣ bid. Even 3♣ is wrong because this bid is non-forcing. South therefore chooses between 2♠, forcing, or a practical 3NT.

South 2 is the right answer. He has no choice but to bid 2♣, his longest suit. His hand is weak but could even have been weaker. Study this situation well. This kind of sequence often derails because North keeps on bidding. Without serious extra strength for his double he should pass 2♣. South knows North has opening strength and yet suggests only a modest 2♣ contract.

South 3 should bid 2♥. North usually has a four-card suit in hearts when doubling 1♠ for takeout. Therefore the best chance of finding a fit is in hearts. Besides: a heart contract pays better than a club contract.