---- Mary looks sad. What _________ her ?
-----She failed in the maths exam.
A. happened to B. happened C. was happened D were happened
Emergencies and unexpected situations happen all the time.
| A．may | B．can | C．must | D．should |
While watching television, .
| A．the doorbell rang | B．the doorbell rings |
| C．we heard the doorbell ring | D．we heard the doorbell rings |
The rising frequency for smoggy days puts me into deep that maybe one day citizens will have to rely on masks to survive.
| A．doubt | B．worry | C．shock | D．faith |
The report has found that more and more Chinese have an American or British temporary visa for holiday spending in recent years.
| A．stood for | B．applied for |
| C．accounted for | D．searched for |
downloading of large numbers of apps is one of the most risky behaviors someone with a smartphone can engage in.
| A．Cautious | B．Public | C．Random | D．General |