guard ·phrase (IDIOM)
Definition: to be ready to deal with something difficult that might happen Level: C2
公司被警告要对可疑包裹保持警惕。
Companies were warned to ___be ___on ___their ___guard for suspicious packages.
然而，我们应该保持警惕，以防情况升级。
However, we should ___be ___on ___guard to prevent situations from escalating.
在不确定时期，投资者需要警惕市场波动。
In uncertain times, investors need to ___be ___on ___their ___guard against market volatility.