LEARNING CENTER

1NT. 15-17 balanced. You do not need to have all 4 suits stopped.

Win the K and duck a diamond. There is no rush to take the club finesse or try for 3-3 spades. If those suits work, they will work later.
If you play those suits now, you risk setting up tricks for the opponents and losing tempo.

Look what happens if you win the K and then take a club finesse:

It loses (if it would have won, so what? You could have always done that later).
Meanwhile, the Q comes back:

Big problems. You will go down. Spades don't split. It is too late to set up diamonds (East's hearts will be the setting tricks).

Because this preserves all of our other chances (spades or clubs) but also brings the potential of 3-3 diamonds into play. There is no reason to release the A in case the diamonds split poorly.

East can win and switch to hearts (nothing else would hurt us)...

We can win and concede another diamond -- still keeping all of our options in play:

Whatever East does (likely more hearts), we now have 3 chances: Spades 3-3, Club finesse, or diamonds 3-3.

Test to see if spades or diamonds are 3-3.
You don't want to risk the club finesse unless you have to. It might lose and East might take too many good hearts.
You can safely test spades and diamonds. Just count to see if they are 3-3.
If they are, that gives you at least 9 tricks. At that point, if you can safely work on overtricks, so be it.

Below is the full deal. You can see that diamonds are 3-3, so your correct line of play (working on diamonds first--developing as opposed to grabbing) lands the contract.

Click here to play Lesson Deal #3.