21.-- Who called me this morning when I was out?
-- A man calling ________ Robert.
A. him B. himself C. his D. 不填
22. Look out ! Don' t get too close to the house __________ roof is under repair.
A. whose B. which C. of which D. that
23. Sorry, Madam. You' d better come tomorrow because it' s __________ the visiting hours.
A. during B. at C. beyond D. before
