necessary
必须───must;必须───must
We must set realistic goals.───我们必须制订可实现的目标。
Why must she interrupt?───她为什么偏要打断呢？
This structure must be stable.───这种结构一定很稳固。
Nor does a cloud alone give a rainbow, there must be the crystal drops to reflect the light of the sun.───单独一片云不会产生虹，必须要有结晶水珠才能反映太阳的光线。
Knowledge is a well-of-the- wisp , fluttering ever out of the traveler's reach, and a weary journey must be endured before it is even seen .───知识是团鬼火，永远飘荡在行人伸手莫及的地方；甚至为了看它一眼，必须作一次使人劳顿不堪的旅行。
The newspaper must be printed on time, the newscast must go on the air, and mistakes cannot be allowed to go through.───报纸必须准时付印，广播电视必须按时播出，而编辑不能放任错误。
Sentencedict.com is a online sentence dictionary, on which you can find good sentences for a large number of words.
As the wind blows, you must set your sail.
Children under 14 must be accompanied by an adult.
You must lose a fly to catch a trout.
We must reinforce the troops at the front.