How long ________they_________ —Sorry, I don’t know. But I know that Mr. Chen is going to _______a nurse next month.

Holly has _____fed the dog, but she hasn’t watered the plants_______.

early for his date, Mark spent time reading thenewspaper

It’s difficult _____ us to remember new words.

There _____a very small number of books on science in our school library, and in these years the number of them growing larger and larger.