We ______ to clean the blackboard every day.
| A．take turn | B．in turn |
| C．by turns | D．take turns |
He even __________ to call the deal off if we didn't satisfy his demands.
| A．scolded |
| B．threatened |
| C．warned |
| D．declared |
Mother has told us to __________ some candles in the house in case the electricity is off. So now we are busy __________ the coming night.
| A．prepare; preparing |
| B．prepare for; preparing |
| C．prepare; preparing for |
| D．prepare for; preparing for |
Some people maintain that watching violence on TV is one of the major causes of __________ behavior and crime in society.
| A．artificial |
| B．automatic |
| C．aggressive |
| D．allergic |
To our surprise, we found the Queen's jewels __________ by special royal soldiers.
| A．guarded |
| B．trained |
| C．impressed |
| D．absorbed |
There is a（n）__________ of plants in the old man's yard, such as trees, flowers and grass.
| A．group |
| B．kind |
| C．amount |
| D．variety |