科学家在实验室里仔细观察化学反应的过程。

Scientists ___observed the chemical reaction carefully in the lab.

她评论说今天的会议很有效率。

She ___observed that today's meeting was very efficient.

所有员工都必须遵守公司的着装规定。

All employees must ___observe the company's dress code.

我们每年都会庆祝国庆节。

We ___observe National Day every year.