______ scientists have learned a lot about the universe, there is much we still don't know.
| A．Once | B．Since | C．Though | D．Unless |
I sooner but I didn’t know that they were waiting for me.
| A．had come | B．was coming | C．would come | D．would have come |
is known to us all is that the 2012 Olympic Games will take place in London.
| A．As | B．What | C．That | D．It |
Was it because of the heavy snowstorm in Europe the flight had to be put off?
| A．which | B．so | C．why | D．that |
In no place of China little about the economic development nowadays.
| A．the local government cares | B．does the local government care |
| C．doesn’t the local government care | D．cares the local government |
Tsinghua University, in 1911, is home to a great number of outstanding figures.
| A．found | B．founding | C．founded | D．to be founded |