Whoever _____a new idea of how to work out the puzzle will be given a prize.
| A．keeps up with | B．puts up with |
| C．ends up with | D．comes up with |
He went home for lunch ____ the clock struck twelve.
| A．while | B．immediately | C．right away | D．at once |
19. Is this the very factory ____ he visited last month?
| A．which | B．that | C．where | D．in which |
The first thing ____ you should do is to learn all the new words by heart.
| A．what | B．that | C．which | D．who |
The students are talking about the strange people and stories ____ they met in the adventure.
| A．that | B．which | C．what | D．whom |
It is not I but Mr. Green who ____ in charge of the company.
| A．is | B．am | C．are | D．was |