Bidding
Partner opens 2NT showing 20-22 HCP , you want to see if your side has a major suit fit so you bid
3C (Stayman convention) asking partner to show you their four card major suits starting at hearts and secondly bidding spades if they have them. Partner bids spades which denies having 4 heart suit cards. Wanting to know what stoppers (Aces) your partner holds
jump to 4NT - saying 'partner tell me about your Aces' partner responds 5C showing all 4 Aces. Bidding 5NT
asks about Kings. Partner replies 5C = no Kings (you know this because you already have 2 so the reply means they have 0 Kings) Bid 6NT with 2 missing kings. Ouch
Acol Bidding
Partner opens 2NT showing 20-22 HCP , you want to see if your side has a major suit fit so you bid
3C (Stayman convention) asking partner to show you their four card major suits starting at hearts and secondly bidding spades if they have them. Partner bids spades which denies having 4 heart suit cards. Wanting to know what stoppers (Aces) your partner holds
jump to 4NT - saying 'partner tell me about your Aces' partner responds 5C showing all 4 Aces. Bidding 5NT
asks about Kings. Partner replies 5C = no Kings (you know this because you already have 2 so the reply means they have 0 Kings) Bid 6NT with 2 missing kings. Ouch
Dummy goes down and you count your winners. 2 in spades, 2 in hearts 4 in diamonds and 3 in clubs. Hmm You will need to finesse west for KS and KH. Hopefully one of them will work!
With a heart lead take the heart finesse! play QH. Lead out JS planning to duck if west does not play KS, but he does, so cover with AS. Play your spades counting oppositions discards, the last spade 9S is still out. Switch to diamonds playing all the ones in your hand and both the clubs in hand before crossing to dummy with AD, play Ac AH and losing the last spade to easts 9S.
Makes 12 tricks. Most people would take the chance that they will be able to finesse or drop one of the Kings and would bid 6NT. But after asking about Kings you don't have any choices left you are committed to slam but you need to choose either 6NT or 7NT.