Who are interested in taking part in it.为何加ed与ing?

Who are interested in taking part in it.为何加ed与ing?

首先,谓语部分可认为是短语be interested in的系表结构加介词短语,interested 可理解为形容词.
其次,因为in为介词所以其后所加动词短语take part in 转化为动名词短语（表主动）.

be interested in 固定搭配，对……感兴趣，前面修饰人Who，后面是因为前面有介词in ，所以用taking

be interested in doing sth 是固定用法‘对……感兴趣‘’

有道词典去