Scientists say it may be five or six years _______ it is possible to test this medicine on human patients.
| A．since | B．after | C．before | D．when |
Everyone wants to live in a beautiful, comfortable and “livable” place, but not ______ know where it is.
| A．all | B．some | C．either | D．both |
______ in color, the garden looks dull in this late fall.
| A．Lack | B．Lacked | C．Lacking | D．To lack |
--- Albert, I have a favor to ask you.
--- _______.
| A．It’s a pleasure | B．Go ahead | C．Help yourself | D．It doesn’t matter |
“The moment ______ soon,” he thought to himself, waiting nervously.
| A．is coming | B．was coming | C．came | D．has come |
______ nearly all behavior is learned behavior is a basic assumption ______ has been put forward by the social scientists.
| A．What, that | B．That, what | C．What, what | D．That, that |