他们必须小心
They have to be careful.
以上为机器翻译结果，长、整句建议使用 人工翻译 。
他们必须小心，不要让自己的孩子对父母感到失望。
They have to be careful not to come across as disappointed in their child.
youdao
所以他们必须小心地限额配给。
So they have to ration it out carefully.
但是他们必须小心地拟定计划，并且善用时间。
But their plans must be made carefully, and their time must be used well.
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