________ the question of how global warming has _________, we are doing some projects at school.
| A．Exploring, come about | B．To explore, come out |
| C．Having explored, come to | D．Being explored, come over |
He ____ his home for a week.
| A．hasn’t left | B．has left | C．was left | D．had left |
--What’s ___ population of China?
--China has ____ population of 1.5 billion.
| A．a; the | B．the; a | C．/;/ | D．the; the |
--what do you think of the film? ---_____?
| A．Excitedly | B．Very well | C．It’s wonderful | D．I think so |
Is ____ dangerous to swim in the river alone?
| A．it | B．this | C．that | D．he |
--___do you clean the reading room?
---Every two or three days.
| A．How long | B．How far | C．How soon | D．How often |