You should be on guard when a stranger comes to your doors.(当陌生人站在你家门前是，你应该有所堤防。)
After all, cities are hyper-social places, in which residents must be constantly on guard, and have mathematically more opportunity to experience stressful interaction.(毕竟，城市是一个具有超社会性质的地方，身处其中的居民们必须时常保持警惕，并且拥有在数量上占优的机会去体验充满压力的相互作用。)
If we are alert enough, we'll notice that we are always on guard.(如果我们足够警惕，你会发现我们经常是在站岗。)
The animal that goes to a favorite food-foraging location and sees signs that a predator was there - but not the predator itself - may be on guard the next time.(在某些情况下，我们会幻想自己的先人又复活了。“一个动物到它最喜欢觅食地点，看到有个食肉动物一在那里的迹象，但不是食肉动物本身，可能是上次（下次）在那里站岗。)
The world is alert and on guard as never before.(世界从没有向现在这样保持警惕和戒备。)
Security was tight around the launch site, where about 1, 600 police were on guard.(安全措施紧密围绕发射场，其中约1600名警察守卫。)
On guard: Mexico City is at a virtual standstill.(站岗：墨西哥处在一个实际意义上的停滞状态中。)
Then they turn gracefully and walk past the two police officers on guard-the officers try not to stare-into the hotel ballroom.(然后，她们优雅的转过身去，走向那些不敢盯着她们的两名警官，然后进入宾馆的舞厅。)
The soldier who is on guard is my friend.(那个站岗的战士是我的朋友。)
Distrust increases tension and negative "on guard" behavior, which can erode the spirit of the team and ultimately productivity.(不信任会增加紧张和消极的“防范”行为，这会破坏团队精神而最终影响生产力。)
