He made another wonderful discovery, ______ of great importance to science.
| A．which I think is | B．which I think it is | C．which I think it | D．I think is |
To learn English well, you should ______ as many words and expressions as possible.
| A．distinguish | B．undertake | C．associate | D．accumulate |
David studied hard before the examination, and it ______. He made an A.
A. worked out B. marked out C. paid off D. got through
______ label to each of the trees, with detailed introduction of their features, and visitors will know more about them and how to protect them.
| A．To attach | B．Attach | C．Attached | D．Having attached |
---Who is to give us the lecture today?
---The lady _____ our headmaster into the hall.
| A．follows | B．following | C．followed | D．to be followed |
Those who don’t get their sufficient sleep are actually sending a(n) _____ to severe problems in their life.
| A．invitation | B．warning | C．explanation | D．solution |