—Kathy and her sister are so alike.—I can’t tell one from ____.
I ________ use a clock to wake me up because at six o'clock each morning the train comes by my house.
What do you mean, there are only ten tickets?There________be twelve.
—________ I take the book out?—I'm afraid not.
Doctors say that exercise is important for health, but it ________ be regular exercise.
One of our rules is that every student ________ wear school uniform while at school.