Without the 
air to hold some of the sun’s heat, the earth at night ____ for us to live.
| A．would be freezing cold | B．will be freezing coldly |
| C．would be frozen cold | D．can freeze coldly |
Just as the tree is the unit of a forest and the book the unit of a library, ______ the molecule is the unit of matter.
| A．as | B．like | C．so | D．thus |
The door opened and in ________.
| A．rushed they | B．the children rushed | C．they rushed | D．did the children rush |
______ nobody was very enthusiastic about it, they decided to cancel the trip.
| A．See that | B．Seeing that | C．So | D．When |
I think our boat can pass the treacherous water ______ cautiously handled.
| A．until | B．if | C．lest | D．with |
The engineers are going on with their highway project, _____the expenses have risen.
| A．even though | B．just because | C．now that | D．as though |