American Indians _______ about five percent of the U.S population.
| A．fill up | B．bring up | C．make up | D．set up |
With the word “PM2. 5” constantly __________ in media reports, you might be wondering what on earth it means.
| A．appeared |
| B．appearing |
| C．to appear |
| D．being appeared |
With the audience __________ at her, the little girl felt nervous on the stage.
| A．staring |
| B．to stare |
| C．stare |
| D．stared |
Half the world's population __________ water shortages within 15 years according to the World Bank, just one of many recent alarming reports on the world's fresh water supply.
| A．are suffering |
| B．have been suffered |
| C．will suffer |
| D．were suffered |
It is reported that in our country cities __________ heavy air pollution that is 30 percent above the national standard or higher should try to meet standards by 2030.
| A．suffering |
| B．suffer |
| C．suffered |
| D．are suffering |
-Is it all right if I sit here?
-__________，sir. The seats are for elderly people only.
| A．Better not |
| B．Go ahead |
| C．As you please |
| D．No way |