______ it have been the failure to pick up directions from the ground control that caused the air crash?
| A．Must | B．Could | C．Would | D．Should |
The vegetables grown in this district are much better than ____ in that district.
| A．/ | B．that | C．ones | D．those |
My chest _____ when I take a deep breath, doctor.
| A．wounds | B．harms | C．hurts | D．injuries |
---Michael was late for Mr. Smith’s oral class this morning.
---______? As far as I know, he never came late to class.
| A．How come | B．So what | C．Why not | D．What for |
As time _______, you’ll learn more.
| A．goes by | B．goes away | C．goes about | D．goes off |
We should do what we can to save those_________ species, for example, the tiger, an animal which was considered_______ to humans.
| A．dangerous; endangered | B．dangerous; in danger |
| C．endangered; in danger | D．endangered; dangerous |