observing

The biologist spent hours observing the rare birds in their natural habitat.

生物学家花了数小时观察稀有鸟类在其自然栖息地中的行为。

She kept observing the stranger from across the room, trying to figure out who he was.

她一直从房间另一边观察那个陌生人，试图弄清楚他是谁。

During the experiment, the assistant was carefully observing any changes in the chemical reaction.

实验期间，助手仔细地观察化学反应中的任何变化。