他昨天很忙，所以没来参加聚会。

He ___was busy yesterday, so he didn't come to the party.

她昨天生病了所以没来上课。

She ___was sick yesterday, so she didn't come to class.

我正在做饭时，门铃响了。

I ___was cooking when the doorbell rang.

蛋糕被孩子们吃光了。

The cake ___was eaten by the children.