Besides proper diet, exercise is one of the key ___________of a healthy lifestyle.
| A．categories | B．components | C．ranges | D．processes |
It will be many years ______the doctors and medical scientists can find _____ for cancer.
| A．since; cures | B．when; treatments | C．before; cures | D．until; treatments |
We have to ______ everything question in detail ______ we take action.
It is clear that no use can be made ______radium _____we don’t know clearly the characteristics of it.
| A．from; if | B．of; unless | C．from; unless | D．of; if |
From my point of view, the theory that ______ by the scientist is not quite scientific.
| A．was risen | B．brought up | C．had been raised | D．was put forward |
The invention of steam engine greatly sped up the industrial revolution, which _____ a lot to the take-off of the world.
| A．led | B．contributed | C．constructed | D．exposed |