1.
"If necessary, I will go myself."
“在必要时，我还可以自己去。”
2.
an actor able to replace a regular performer when required.
在必要时能够代替正规演员的演员。
3.
In times of necessity, you comrades present here will have to live in sheds.
在必要的时候，在座的同志们要住棚子。
4.
If need be , I can do extra work at the weekend
必要时我可以在周末加班
5.
You have to be very loose-limbed to do gymnastics well.
要做好体操，你必须在做时非常柔软。
6.
Be sure to slow down on stairs and escalators.
在楼梯与电扶梯时务必要降慢速度喔！
7.
If need is, I can do extra work at the weekend.
必要时我可以在周末加班.
8.
If you want to play football, you'll have to do it on your own time.
如果你要踢足球，必须在课余时间踢。
9.
Well, really! You needn't have said that.
咳,真是的!你当时实在没有必要那么说。
10.
If you need to, refer back to the passage for clarification.
你可能在必要的时候得重回文章定位。
11.
It is necessary to retain the Special Committee because sometimes the Front Committee has to move about with the troops.
特委仍有存在的必要，因为前委有时要随军行动。
12.
Attention must be paid on the synergic effect of smoking and silicosis in cancer complication.
吸烟和矽肺同时存在时,有必要注意协同作用。
13.
I cannot tell you, but I put in a lot of extra time when I think it is necessary.
我不能告诉妳﹐但在必要的时候我也会超时工作。
14.
In the ebb and flow of political struggle, it was inevitable that one of them would go down.
在时起时伏的政治斗争中，必有一派要失败。
15.
Read no letters, books, or papers in company; but when there is necessity for doing it, you must ask leave.
在客人面前不要读信、书或读报；有必要这样做时，必须道声失陪。
16.
“We live in an age when unnecessay things are only necessities.
我们生活在一个把不必要的东西当成非常必要的时代。
17.
Apparently, the government's current reform of the teaching of Chinese is very essential, most timely and definitely in keeping with the new age.
现在政府改革华文教学，可说是十分必要，非常及时，也是时代的必需。
18.
( The serve must be played from behind the baseline and must land in the service box.
（球时选手必须站在底线之外，球必须要落在对方的发球区内。