—Who______ it be that is knocking at the door? —It ______ be Father, but I’m not sure.
27. How can you expect him to make any progress ____ you never give him a chance to have a try?
26. They got married 30 years ago and never ______ in the past years.
25. The student who was caught ______ in the exam has been removed from school.
24. ---Is there any flight to New York?--- I think there ______ be, for it is snowing so heavily.
23. We have no idea at all ______the economic crisis will end.