Answer
You (East, 3rd seat, none vulnerable) are defending against South’s two diamond contract (partner, West, made a takeout double of South’s one diamond opening bid):
Partner leads the King of spades (three, seven, Ace). Declarer leads the seven of clubs (four, ten, Ace) and you return the nine of spades to the Jack and partner’s Queen. Partner cashes the ten of spades and everyone follows. Now partner leads the Jack of clubs to dummy’s Queen; declarer throws a heart. Now the King of clubs; declarer throws the Jack of hearts and partner follows. Now a heart to declarer’s Ace and the King of diamonds to partner’s Ace. Partner leads the 13th spade.Will you play a heart, or will you ruff? Perhaps because this is a quiz, probably you figured out that you need to ruff. To see why, have a look at the updated diagram on the next page, showing the position when West is about to lead the last spade (five cards remain, declarer has won four tricks and lost four):