我们只需要再多一个人就能玩游戏了——你能说服你妹妹加入吗？

We only need one more person to play the game - can you persuade your sister to ___join ___in?

如果你会唱这首歌，我们希望每个人都加入合唱。

If you know the song, we'd like everyone to ___join ___in on the chorus.

起初我不感兴趣，但我决定加入。

I wasn't interested at first, but I decided to ___join ___in.