Translation of "Observed" in Chinese

How is the error observed?

错误是如何显示出来的？

The boy observed the birds all day.

男孩观察了一整天鸟。

The change is too small to be observed.

变化太小，察觉不出来。

The rule of the road must be strictly observed.

道路法规必须被严格遵守。

We observed this plant closely for a few weeks.

我们密切地关注这家工厂几个星期了.