24. The room ________ once a day.
a. should clean b. should be cleaning
c. should be cleaned d. should have cleaned
25. Two tablets ________ twice a day to have you recover from the illness quickly.
a. must take b. must be taken c. must have taken d. must be taking
26. Theresa walked past me without saying a word. She ________ me.
a. can't have seen b. can't see
c. can't have been seen d. can be seen