Rolls-Royces is ranked fourth in the list of best cars．The Browns already have two and now they are buying third．
| A．the ; the | B．不填; a | C．the ; a | D．不填; the |
It ________ some time _________ I realized the truth.
| A．was; before | B．is; before |
| C．has been; until | D．has been; after |
The annual Energy & Environment Conference calls on our human beings to _______environmental issues.
| A．care for | B．care of | C．care about | D．care in |
--- We need someone to host the New Year Party.
--- ________ the handsome young man have a go?
| A．Need | B．Must | C．Shall | D．Will |
Being a teacher always encouraging students to think for themselves, I won't tell them answers until they __________ on a math problem for more than an hour.
| A．have worked | B．will have worked |
| C．will have been working | D．had worked |
He could speak English fluently because he __________ it for four years when he was a college student.
| A．had studied | B．have been studying | C．studied | D．was studying |