Answer: Bridge Problem 6

The contract can be defeated with the lead of the ♦4. If declarer plays the ♦A and plays trump, East will win the ace of spades and play a diamond to the queen and West will return a heart. South must win (or else West will ruff the next heart for the setting trick), but then there is no way to avoid two more losers, a heart and a diamond.

If declarer ducks the opening lead, East wins the ♦K and plays the ♥K. South must win (or else another heart gets ruffed by West and the trump ace is the setting trick), but East, when in with the trump ace, cashes the ♥Q, with West throwing the ♦Q, and then West ruffs a diamond for the setting trick.

Note that if the opening lead is the ♦Q, declarer will win the ace and play trump. East can take the ace, cash the ♦K and play another diamond for West to ruff, but declarer can then pitch a heart on the fourth diamond and cross ruff the rest to come to ten tricks.