Not until the teacher explained the importance of getting up early ______ we promise to come early.
| A．should | B．would | C．did | D．could |
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 |
Looking at my mother's ___________ face, I regretted not having told her my whereabouts on the phone.
| A．worrying | B．worried | C．anxioused | D．satisfied |