You chose to play the King of Diamonds.This is the correct answer. You have played, Third hand high, and if Declarer wants to win the trick, he will have to use his Ace.
And of course, that is what Declarer will do. Declarer has now won 4 tricks and lost one. He needs to take out the remaining Trump trick from the opposition, which he now does by playing the King of Clubs from his hand. West has to play the 7 of Clubs; Dummy plays low with the 4 of Clubs, and East, having no Clubs left will discard. In a later lesson, we will talk about significant discards, but for now, we will just have him throw away a useless card, the 3 of Hearts.
And the rest of the tricks now belong to the Declarer. The Queen of Diamonds is a winner, and he will put the 8 of Diamonds from the Dummy on it. West plays the 9 and East the 2.
Since Dummy now has no remaining Diamonds, Declarer can play the 6 of Diamonds, West plays the Jack, and Dummy trumps it with the 6 of Clubs, East playing the 3 of Diamonds. This procedure of winning tricks that we are now going to use is called CROSS TRUMPING OR CROSS RUFFING.
Now from Dummy, Declarer leads the 10 of Hearts (actually they are all equal in his hand) and West has a bit of a dilemma.
West's Heart holding is as follows: A,Q,5,3
It will be remembered that the Jack of Hearts was thrown away by Declarer on an earlier round. But we don't know where the King of Hearts is.
14. Which of West's hearts should he play?