Polar explorers have to be extremely _____ to bear the climate and other hardships.
| A．tough | B．rough | C．difficult | D．brave |
I’m willing to lend you a hand__________busy I’m for the moment.
| A．because | B．but that | C．but | D．however |
—__________you like the car so much，why not drive it back?
—Well，I can’t afford__________car.
| A．Now that; that big a |
| B．If; such big a |
| C．When; so a big |
| D．So long as; that a big |
__________there are only 20 minutes left before the train left，I felt uneasy in the taxi to the railway station.
| A．That | B．When | C．Which | D．Because |
__________ problems you have，you can always come to me for help.
| A．What | B．Whatever |
| C．Whenever | D．Which |
Plants grow best__________it is warm and wet.
| A．which | B．in which | C．where | D．that |