It's necessary

有必要───be necessary;有必要───be necessary

We have already agreed that secrecy may be necessary.───我们统一了意见,认为需要保守秘密.

I don't imagine that will be necessary. Leastways, I hope not.───我想那是不必要的。至少，我希望不是。

It may be necessary to buy a new one.───也许有必要买个新的了。

adjustment of the lens may be necessary.───可能需要调整一下镜头。

In several cases, additional sedation may be necessary.───对于严重的病例, 还必须镇静.

Spraying with insecticides and fungicides may be necessary to control any insects and diseases.───也许有必要喷洒杀虫剂和杀菌剂以防止病虫害.

The ability to do this will be necessary in future flights to distant planets.───将来飞往遥远的行星时,需要这样的能力.

If God did not exist, it would be necessary to invent Him. 

It will be necessary to proceed with caution.

Irrigation measures will be necessary in areas of erratic rainfall.

It may be necessary to make alternative arrangements.

At least a year's preparatory work will be necessary before building can start.