We have informed the airport to be on alert as the ash is quite high this time.

克里斯蒂安托说：“我们已经通知机场时刻警惕，因为火山灰现在已经上升到高空。

youdao

Although they may appear dead, they sometimes spring up to attack, so always be on alert.

它们也许看上去已经死去，但有时它们也会奋起战斗，时刻处于警戒状态。

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Therefore, in international trade, business people should be on alert against different local customs and business norms.

因此，在国际贸易中，商人应密切注意不同地方的风俗和商业准则。

youdao

General Fonseka,in the letter, says Sri Lanka asked India on October 15 to place troops on alert in case they would be needed to intervene to foil a coup on the island.

VOA: standard.2009.11.14

It was after lunch that teachers first got word to be on alert for severe weather.

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Thus, policymakers and informed citizens always need to be on alert for exaggerated claims regarding the benefits of Medicaid expansion.

FORBES: Will Medicaid Expansion Create Jobs?

According to Israel's army radio, army chief Lieutenant General Gaby Ashkenazi had ordered ground, air and naval forces to be on alert.

BBC: New security measures could remain in place for months