Second Answer
Against three notrump, you led the six of clubs (four, ten, Ace). Clearly declarer has the King and nine of clubs also. Declarer cashes the Ace and King of spades (partner follows) and leads the Jack. This position remains (it’s your play).
What will you discard to this trick: a heart, a diamond, or a club? Declarer showed 18-20 HCP and has already shown up with Ace-King of clubs and Ace-King-Jack of spades (15 HCP). Declarer has only another 3-5 HCP in the red suits. Partner must have strength in diamonds, so you can spare a diamond. However, if declarer has four hearts to the Ace (or three to the Ace-Jack), you cannot afford to discard a heart. Discard a discouraging diamond.
You will be under pressure if declarer cashes the two additional spade winners from dummy. You’ve already noted that you can’t afford to discard a heart.
As you expected, declarer cashes dummy’s two remaining spade winners. What will your two discards be: two diamonds, one diamond and one club, or two clubs?