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. When I got back home I saw a message pinned to the door, ______ “Sorry
to miss you; will call later.”
A. read B. reads C. to read D. reading
