(a) Dummy
♦ K Q J 10 4 East (you)
♦ A 9 5 3 2

As East, retain all your five diamonds if you can. Throw one away and, after your ♦ A is forced out, all dummy’s remaining four cards will be good including, crucially, ♦ 4 on the fifth
round.

(b) Dummy
♣ A Q J 6 East (you)
♣ K 10 5 2

As East, throw a club away and dummy’s clubs will provide three tricks; you will only score ♣ K.

(c) Dummy
♥ A K Q 5 East (you)
♥ 6 4 3 2

Your hearts are dreadful. Yet because your ♥ 6 beats dummy’s ♥ 5 on the fourth round, you must retain them all. [Swap ♥ 5 and ♥ 6 and you could throw them all away as your highest card would be lower than dummy’s lowest card].

(d) Dummy
♠ A K J 5 East (you)
♠ Q 10 7 3 2

You can discard one spade – bringing you down to the same length as dummy; but you must not throw any more away.

(e) Dummy
♦ A 7 5 East (you)
♦ Q 9 4

The need to keep equal length with dummy is less acute here. Unless declarer has five diamonds, partner will be able to guard the suit.

Take East's hand to find the key discard