例句：

They danced and danced until a lot of us joined in. 他们不停地跳着舞, 直到我们中间许多人都参加了进去。

Do you know how many of them joined in the research project? 你知道他们中间有多少人参加了这项研究项目吗?

Would you join us in a walk? 你不同我们一起散步吗?

John takes part in many school activities. 约翰参加很多学校里的活动。

Joe took an active part in the struggle. 乔积极参加斗争。

The whole sales force attended the conference. 整个销售界的权贵都出席了这次会议。

All children are required to attend school. 所有的孩子都必须上学。

His son joined the army last year. 他儿子去年入伍。