A regiment stayed behind to keep guard on the frontier.

有一个团留下来防守边境。

All of them are kids? Why do they have got to keep guard for the kids?

都是小孩子吗？天使为什么要守着小孩呢？

The policemen keep guard at the airfield and watched every body carefully.

警察们马上在停机场守候，并且仔细的盯着每一个人。

We must keep our resolve. And we must never let down our guard.

我们不能骄傲自满，我们要坚定决心，我们绝不能放松警惕。

Generally, these attacks have been relegated to the category of annoyance, but don't let that be a reason to lower your guard, because there are plenty of other things to keep you up at night.

通常，我们认为这是一种无聊的攻击，但您一定不要因此放松警惕，因为它造成的许多问题会让您半夜睡不着觉。