Game in NT or Major?
Bidding: North opens 1♣ – 1♠ – 2♦ – 3NT – all pass
MrQ: Could South have bid 3♠ instead of 3NT to show 6 card spade suit, just in case there was a fit in spades?
Guru: South’s 3NT bid is a terrible bid. While North does have a very good reverse, I would probably have bid 3NT which despite the singleton ace of spades shows the real strength of the hand. With not great spades but six of them, and a singleton club, South should then bid 4♠. But given the reverse, all South has to do is to bid 2♠ because “a reverse is forcing to 2NT” so no harm in bidding 2♠. That can not be passed. Then the bidding continues 3♥ from North and South knows the exact shape of North and can now bid either 3♠ (still forcing and now a six card suit) OR 3NT knowing that it may well be a better contract than 4♠. If South bids 3♠ in that sequence North should bid 4♠ not 3NT.