-- I'd like to invite you to a party tomorrow evening.
-- Thank you, but ______ I'll be free I'm uncertain.
| A．while | B．if | C．when | D．whether |
Humans are destroying nature day by day, ________, of course, will cause punishment sooner or later.
| A．that | B．/ | C．which | D．What |
The school _______ I visited the other day was not the one _______ I once studied.
| A．that; which | B．which; where | C．where; which | D．where; where |
Is this the reason____ at the meeting for his carelessness in his work?
| A．he explained | B．what he explained |
| C．how he explained | D．why he explained |
You stepped into the lab with your shoes on? You’re _______ to take them off before you enter it.
| A．invited | B．supposed | C．forbidden | D．permitted |
—We could invite John and Barbara to the Friday night party.
—Yes, ______ ? I’ll give them a call right now.
| A．why not | B．what for | C．why | D．what |