The boy who is playing football over there is ___
| A．a my friend | B．one of my friend | C．a friend of mine | D．a friend of me |
Hardly ___________the door when he rushed into the office out of breath.
| A．I opened | B．did I open | C．I had opened | D．had I opened |
We want such materials ________ can bear high temperature and pressure.
| A．that | B．as | C．what | D．which |
Space exploration has been made ______ with the development of modern science and technology.
| A．it possible | B．it was possible | C．that possible | D．possible |
A mysterious illness, referred to as “ a typical phenomena”, has been brought under control, the government said on Wednesday, ______ no cause of it has been made public.
| A．though | B．when | C．that | D．because |
Before leaving home, make sure to turn off the electricity, lock the door, ______ the windows open.
| A．and not to leave | B．instead of leaving |
| C．rather than leave | D．and not leave |