The old man was quite weak after the operation, so he must ___________well.
—What do you usually do in the morning? —I often practice English.
In those days bikes were not ______ used because few people could afford (负担起) to buy one.
Jenny keeps two pets. One is a dog, ______ is a rabbit.
Which of the following signs is used to tell people to save water?
He was ______ tired ______ go on walking.