—Who______ it be that is knocking at the door?—It ______ be Father, but I’m not sure.
The manager found that his office ______ the day before.
Although new problems ______ during the last experiment, they didn’t give up.
Some people always take seriously the ______ of the complete globe end in the near future.
— Did you visit the museum today? — No. We ______ it, but we spent too much time shopping.
I am going to do ______ I can ______ him a good impression.