作用力与反作用力大小相等，方向相反，作用在一条直线上.作用力与反作用力的性质必定

Many other new techniques are now available that enable more research(do) in the test tube to see if chemicals produce harmful biological effects.

He took his umbrella with him lest it(rain).

Every boy and girl(treat) in the same way.

Robots,(become) increasingly prevalent in factories and industrial plants throughout the developed world, are programmed and engineered to perform industrial tasks without human intervention.

One hundred miles(be) too far to travel on foot.

I would rather you(come) tomorrow.

Although they agree that life is important and should be respected, they feel that the quality of life should not(ignore).

If you had been in better health, we(allow) you to join them in the work.

The theory of black holes in space(accept) by many serious scientists and astronomers.