----Have you been to the Summer Palace?
----Perhaps not in my memory._______, it might have been during my early childhood
| A．If any | B．If ever | C．If only | D．If not |
Scientists think they have _____ in their attempt to find the causes of some major dieases.
| A．broken through | B．worked out |
| C．fallen out | D．got round |
If you ever have the _____ to go abroad to work, you should take it.
| A．possibility | B．offer | C．luck | D．chance |
In aerospace devices the weight of the necessary power producing equipment is _____.
| A．vital | B．possible | C．capable | D．reliable |
Stressful environments lead to unhealthy behaviors such as poor eating habits, which _____ increase the risk of heart disease.
| A．in turn | B．in return | C．by chance | D．by turns |
The family is a cooperative enterprise for which it is difficult to _____ rules, because each family needs to work out its own ways to deal with its own problems.
| A．set up | B．put down | C．keep up | D．lay down |