---- I usually take a walk at night.
---- ___ do that.
| A．Better not | B．You'd better not to | C．You hadn't better | D．Best not to |
The international agreement, __________to help people kick off the habit of smoking, was signed two years ago.
| A．intended | B．intending | C．intends | D．to intend |
The fact has worried the people across the world ___________ the earth is becoming warmer and warmer these years.
| A．what | B．which | C．that | D．where |
Bob would have helped us yesterday, but he ____________.
| A．is busy | B．had been busy | C．has been busy | D．was busy |
The girl arranged to have piano lessons at the training center with her sister ________ she would stay for an hour.
| A．where | B．who | C．which | D．what |
I have told you the truth. ________ I keep repeating it?
| A．Must | B．Can | C．May | D．Will |