You must act boldly and confidently.

你必须表现得大胆、自信。

《柯林斯英汉双解大词典》

But you must act instantly or be left.

但你必须立即采取行动，或留下。

youdao

He advised, "You must act accordingly."

他建议到：“您必须相应地采取措施。”

youdao

Lincoln said. "You must act."

VOA: special.2009.09.17

Moderation is this wonderfully great important thing for the Greeks.You must act in moderation.

谦卑对希腊人来说是很重要的品质,人必须表现得谦逊

耶鲁公开课 - 古希腊历史简介课程节选

If you don't plan to travel, you must act even faster, and it will cost you.

BBC: Q&A: Euro cash in the UK

In connection with your use of our Services, you must act responsibly and exercise good judgment.

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We too can get caught up in it, the fervor of last minute infomercial deals, but you must act in the next 20 minutes!

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