Not only is it valid, it must be valid. And why is that?

不只有效，而且肯定有效，为什么呢？

youdao

KAREN: a prescription must be valid. It cannot be an expired prescription.

凯伦：处方必须是有效的，不可以是过期的处方。

youdao

Your tests must be valid and reliable; in other words, your tests must be repeatable.

测试必须是有效且可靠的；换言之，测试必须是可重复的。

youdao

What must this experiment have the potential to do, to be a valid scientific experiment?

实验必须有做什么的能力,才能被称为一个有效的科学实验呢？

麻省理工公开课 - 计算机科学及编程导论课程节选

Each must be given a scientifically valid name, usually in Latin or in Greek, that will endure.

WSJ

Among other things, the exchange, which says it handles 80% of all bitcoin trading, said accounts must be verified with a valid photo ID and proof of residence.

WSJ: 'Virtual' Currencies Draw State Scrutiny

Any payments to contractors must be "correct and valid", the report stressed, and only made after proper scrutiny and a broader assessment of what constituted value for money.

BBC: Job centre