--I want to know when Mr. Brown will arrive.--When he , I will tell you. A. will arrive B. arrived C. arrives
—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.