她建议他在谈判期间不要放松警惕。

She advised him not to ___let ___his ___guard ___down during the negotiations.

这位侦探从不放松警惕，即使在下班时也是如此。

The detective never ___lets ___his ___guard ___down, even when off duty.

经过多年的竞争，他终于放下了戒备，提出了休战。

After years of rivalry, he finally ___let ___his ___guard ___down and offered a truce.