it

I found a wallet and returned it to the police station.

(Chinese) 我捡到一个钱包并把它交还给了警察局。

The cat saw the mouse and immediately started chasing it.

(Chinese) 猫看到了老鼠，立刻开始追它。

It is already ten o'clock, so we should go to bed.

(Chinese) 已经十点钟了，所以我们该上床睡觉了。

It is raining heavily outside, so don't forget your umbrella.

(Chinese) 外面雨下得很大，所以别忘了带伞。