He has made another wonderful discovery,___ of great importance to science.
| A．who I think it | B．which I think it is | C．that I think is | D．which I think is |
While working in the countryside , the students ________ a great deal of knowledge on plant life.
| A．looked up | B．picked up | C．put up | D．called up |
By the time she ________ tomorrow, the work ________.
| A．arrives ; will be finished |
| B．arrives ; will have been finished |
| C．will arrive ; will have been finished |
| D．arrives ; will have finished |
Some people waste a lot of food ________ others haven’t enough to eat.
| A．however | B．when | C．as | D．while |
. School children must be taught how to deal with dangerous ________.
| A．states | B．conditions | C．situations | D．positions |
The survey shows that ______ of the population in the country ______ adults.
| A．three fifths; is | B．three fifths; are |
| C．three fifth; are | D．three fifth; is |