—Is your mother _________ English teacher?—No, she isn’t. She is _________doctor.
The librarian told us that we could borrow at most three books __________.
— Why do English people talk so often about the weather when they start a conversation?— Because the weather is a __________ subject.
Checking your answers before handing in your paper can help you __________ mistakes.
It’s kind __________ Yao Beina to donate her corneas (眼角膜) _________ three people in need.
Many people do not realize the importance of health __________ they have fallen ill.