The scientist’s many years’ careful observation ____ a surprising discovery.
| A．ran into | B．began with | C．led to | D．came from |
When ________ to danger and conflict, men tend to increase blood pressure, ________ nervous and anxious.
| A．exposed; felt | B．exposed; feeling | C．exposing; feeling | D．exposing; felt |
It’s too bad that I failed in the math exam. If only I ______ hard at it!
| A．worked | B．had worked | C．has worked | D．would work |
The last decade of the 21st century ________ the rapid, steady development of China in various fields.
| A．witnessed | B．was witnessed | C．is witnessed | D．had witnessed |
---He should have been warned of the danger.
---_______, but he wouldn’t listen to me.
| A．So he had | B．So had he | C．So was he | D．So he was |
The teacher asked the two students to discuss the question in a low voice ________ they should bother the others.
| A．so that | B．in case | C．in order that | D．now that |