You answered the Queen.This is the correct answer.Although technically it doesn't make a lot of difference if you play small and then put a big card up in Declarer's hand, with this particular holding, it is best to lead a high card from the hand where you have the fewer cards in the suit.
So far, you have lead the Queen of Clubs. West has no choice, but plays his singleton 10 of Clubs. Declarer, not wanting or needing to double up, will play his lowest card, which is the 2 of Clubs, and West, will win the trick with the Ace of Clubs.
This time East and West have won, and they collect the trick. The convention is for the partner of the person who won the trick to collect it, and from then on in that hand he collects all the tricks for the partnership. So East makes a little pile of the 4 cards and places it face down in front of him.
Now since West won this trick, it is up to him to lead to the next trick. Here is the remainder of his hand. He also has to keep in mind what has happened so far in the play. One thing that was significant was that Declarer discarded a high Heart on one of his winning (BOSS) Spades. This would indicate that probably Declarer has no Hearts now left in his hand and will be trumping Hearts if they are played.
12. Which of the following cards would be the best for West to now lead?
a. King of Hearts
b. 5 of Diamonds
c. 7 of Spades