The losers - Trumping in Contract

Contract: 4
Lead: Queen of Diamonds

			K 10 9 6
			8
			K 7 5 2
			10 7 6 2
	8 2	N W E S			4
	Q 9 4 3 2				K 10 7 5
	Q J 10				A 9 6 3
	K J 5				Q 8 4 2
			A Q J 7 5 3
			A J 6
			8 4
			A 9

The bidding:

Check that North-South bid the right contract of 4 (advice 9.1). West must lead the Queen of Diamonds (advice 9.2). The declarer play King from dummy which is taken by the Ace of East who re-leads to the 10 and Jack of West which is trumped by the declarer…
In theory this contract should be won without difficulty so long as your pupils have trumped the losing Hearts in hand with the two remaining trumps in dummy after having played them twice.

The interest of this deal is to teach them to divide losers into two categories:

inevitable losers, i.e. those which you cannot win (advice 9.3)
transformable losers, i.e. those which must to transformed into winners.

The deal above allows you to illustrate this theory by finding the losers in South's hand and putting them into the two categories indicated:

inevitable losers: the two Diamonds already led; the9 of Clubs (advice 9.4);
transformable losers: the Jack and 6 of Hearts that can be trumped by dummy's trumps (advice 9.5).

Today we will settle for the following principle: