I don’t think it is a good way. Can you ____________another one?
—Have you finished your homework?—Not _____. There are still some exercises to be done.
_____ the environment is important for human beings.
This is the most beautiful park I have _____ visited.
Xi’an is a city with many places of interest and __ tourists come here every year.
—_____ you _____ your homework yet?—Yes, I _____ it ten minutes ago.