We have to observe carefully what's going on there.
我们必须仔细观察那里的动静。
He made a telescope through which he could observe the stars.
他做了个望远镜,用其观察星座。
All citizens should observe traffic rules.
每位公民都应该遵守交通规则。
We should observe the proprieties.
我们应该遵守礼节。
If they have to leave home, they must wear a face mask and observe good personal hygiene.
若外出,要佩戴口罩,注意个人卫生。