Question

—What are you doing?
—I'm     the key to the door

1. A.
   finding out
2. B.
   looking after
3. C.
   looking for

Answer 1

C
词义辨析题。Find out意为“找到”；look after意为“照顾”；look for意为“寻找”，根据句意可知“我在寻找门上的钥匙”。