21. ----Have you seen _____ pen? I left it here this morning.
----Is it ____ black one? I think I saw it somewhere.
A. a, the B. the, the C. the, a D. a, a
22. The police are looking for a missing boy, who is believed _______ a white pullover and a blue jeans.
A. wearing B. to be wearing C. to wear D. having worn
