一道英语语法题,

问题描述:

一道英语语法题,
Mrs Smith and her twins ( )the dancing club.
A.is going to join B.is going to join in C.are going to join D.are going to join in
求答案并分析

我觉得应该选C
主语是 Mrs Smith and her twins 所以 be动词应该用 are
加入的是俱乐部 应该用 join 例如 join the party
如果是某活动 或 人群 用join in
个人观点 如错见谅