The conductor reminded passengers to keep on guard against the thief.

售票员提醒乘客谨防小偷。

And today, NATO countries are on guard against moves by Russia.

今天，北约国家对俄罗斯的行动保持警惕。

Major ports on India's east coast are on guard against an incoming storm.

印度东海岸的主要港口对即将到来的风暴保持警惕。

Cybersecurity specialists are also expected to be on guard against the hacking of computerized election systems in some states, including Colorado.

预计网络安全专家也将保持警惕，防范科罗拉多等州的计算机选举系统遭到黑客攻击。

But at the outset it seemed necessary to be on guard against the other two.

但一开始似乎有必要提防另外两人。

Millions of people in Africa are on guard against violence and threats of violence by extremists.

数以百万计的非洲人正在警惕极端分子的暴力和暴力威胁。

The animals can weigh up to 20 pounds so the Miami National Weather Service told people to be on guard against raining reptiles.

这些动物可能重达 20 磅，因此，迈阿密国家气象局要求人们提防可能落下来的爬行动物。

If you use all your available storage space and are constantly on guard against clutter, there's plenty of room.

如果您使用了所有可用的存储空间并经常防止杂乱无章，那么空间就足够了。

Experts say that's also possible, though world leaders are likely to be more on guard against ISIS in the future.

专家表示，这也是有可能的，尽管未来世界领导人可能会更加警惕伊斯兰国。

With the Lunar New Year set to begin on January 25, the WHO called on Thai officials and the public to be on guard against the virus.

随着农历新年将于1月25日开始，世卫组织呼吁泰国官员以及公众警惕这种病毒。