All of the flowers now raised here have developed from those _____ in the forest.
| A．once they grew | B．they grew once | C．that once grew | D．once grew |
Though we have been staying up for days, there’s still _____ work remaining to be done.
| A．a large sum of | B．a plenty of | C．a large amount of | D．a large number of |
It is strange that the small boy _________ work out such a difficult exercise, which is even hard to settle for adults.
| A．should | B．might | C．could | D．would |
His wife has left him, but he behaved _______ nothing had happened.
| A．even though | B．as soon as | C．as though | D．as long as |
Clearly, in a system _________ every decision is made on the basis of tradition alone, it may be difficult to achieve progress.
| A．that | B．when | C．where | D．which |
Suddenly it _________ to me that I should report the accident to the police.
| A．happened | B．struck | C．occurred | D．hit |