21．-- Would you like to visit Shantou City with me this summer vacation?
-- No． I ________ it before． Besides, it's hot and humid in summer．
A．visit B．visited C．will visit D．have visited
22． —What’s wrong with your left hand?
—I got it ______ in the door．
A．catching B．caught C．to be caught D．to catch
23．We asked John and Henry some easy questions, butof them could answer them．
A．none B．neither C．all D．both