—You didn't wait for Mr. Smith last night, did you?
—Yes, but we ________. He didn't return home at all.
| A．don't have to | B．needn't have |
| C．didn't need to | D．should have |
To keep healthy,Professor Johnson cycling as a regular form of exercise after he retired.
| A．caught on | B．set out | C．made for | D．took up |
The central provinces have floods in some years，and .
| A．others in droughts | B．droughts in other |
| C．in others droughts | D．droughts in others |
One of the sides of the board is going to be painted yellow，and .
| A．the other is white | B．another white | C．the other white | D．another is white |
This is an illness that may result in total blindness if .
| A．being left untreated | B．left untreated |
| C．not left treating | D．not having left untreated |
—Excuse me.Did you notice whether the No.108 Bus had gone by?
—NotI’ve been standing here.
| A．as | B．when | C．since | D．while |