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 it is |
With ______ successful launching of Tiangong-1, China’s space dream has taken ______ step closer to reality.
| A．the; a | B．/; a | C．a; the | D．the; / |
The speed ______ Tom drives his car is too high.
| A．in which | B．at which | C．at that | D．in what |
With trees and grass_____ about 35％ of the urban area，the city of Hefei has taken on a new look.
| A．covered | B．being covered | C．to be covered | D．covering |
Process so far has been very good．______，we are sure that the project will be completed on time．
| A．However | B．Otherwise | C．Therefore | D．Besides |
— When do we need to pay the balance?
— ____ September 30.
| A．In | B．By | C．During | D．Within |