Which South hand fits the bidding best?

Solution

This jump is special, since South reopens the bidding: he bids fourth in hand over two passes.
In general, a reopening bid can be made on a weaker hand than second in hand, directly over the opening bid (but see *). The reason is, that South knows the opponent's combined point count is limited and so North is bound to have some strength (note: we're discussing a situation where South is rather weak; the more he has, the less certain it is that North has 'something').

If NS play intermediate jump overcalls (13-16 HCP, six-card suit) second in hand, South can bid 2♥ here on a little less, about 11-15 HCP and a six-card suit.
* If, however, NS play weak jump overcalls second in hand, they should not do so fourth in hand! Jumping pre-emptively — disturbing their bidding — against opponents who have already stopped bidding, is obviously pointless; if South fears the hand to be NS's, he should pass!

South 1 has the perfect hand for the jump bid fourth in hand. He shows opening strength (possibly slightly weaker) and six hearts. Pairs will perhaps disagree about the exact points range, but about 11-15 HCP seems to be reasonable.

South 2 is a heart short and has a spade too many to bid 2♥. With this point strength he does best to start by doubling. If partner bids spades (or hearts!): fine. If partner bids something else, South bids hearts cheaply. In that case — he doubles first and cockily bids his own suit next — he shows a hand that is too strong for an immediate 1♥ overcall (1♥, yes: after all, he has only five hearts, so a jump in hearts is out of the question, whether immediate or after doubling first). Fourth in hand this sequence is a little less strong (from about 15 HCP) than in the direct position, second in hand (then it shows 18-up).

South 3 is too strong for the jump to 2♥. He does better by bidding an unorthodox direct 4♥. True, NS may miss a slam this way, but the chance of that is slim after West's opening and North's pass. South should be wary of EW finding a spade fit, which they very well may have in view of South's singleton.
Still, it is not unreasonable to start with a double.
A third alternative: some would jump directly to 3♥, stating this means: 'I am a bit too weak to bid 4♥ directly.' This may look odd, but keep in mind that there is no such thing as a pre-emptive bid in this situation. Still the hand looks less suited for such a bid: it shows a somewhat weaker hand with a seven-card suit.