21. Those letters ________ now. You can do the typing later.
a. need typing b. needn't be typed c. need to type d. needn't typing
22. The museum is open to everybody. It ________ between 9am and 5pm.
a. visits b. visited c. can visit d. can be visited
23. The train ________ by bad weather. I am not sure.
a. might delay b. might be delaying
c. might have delayed d. might have been delayed