How much more expensive do you think a flat in a downtown area is than ______ in a suburban area?
| A．one | B．the one | C．that | D．those |
______ we are doing has never been done before.
| A．That | B．What |
| C．Which | D．Whether |
_______ she couldn’t understand was ______ fewer and fewer students showed interest in her lessons.
| A．What; why | B．That; what |
| C．What; because | D．Why; that |
It is pretty well understood _______ controls the flow of carbon dioxide in and out the atmosphere today.
| A．that | B．when |
| C．what | D．how |
Country life gives him peace and quiet, which is ______ he can’t enjoy while living in big cities.
| A．that | B．why |
| C．where | D．what |
“What were you trying to prove to the police？” “___ I was last night.”
| A．That | B．When |
| C．Where | D．What |