他静静地观察着孩子们在公园里玩耍。

He quietly ___observes the children playing in the park.

她指出天气开始变冷了。

She ___observes that the weather is getting colder.

所有司机都必须遵守交通规则以确保安全。

All drivers must ___observe the traffic rules to ensure safety.

我们家每年都会庆祝圣诞节。

Our family ___observes Christmas every year.