join的用法和搭配 這裏有具體的詳解

1、表示【加入/參加（組織或團體）】，是及物動詞，直接用【join sth】，英語解釋爲If you join an organization, you become a member of it or start work as an employee of it. 例如：

join the league/army /party入團/參軍/入黨

2、表示【參加某種活動（多指正在進行的活動）】，英語解釋爲If you join an activity that other people are doing, you take part in it or become involved with it. 參加 (活動)。

3、搭配有兩種：join sb (in sth)【If one person joins another, they move or go to the same place, for example, so that both of them can do something together. 和…一道】；join sb in doing sth

例如：We'll go to the beach for a sunbath,will you join us?；Will you join us in the game?；Will you join us in play basketball?可見，當表示【加入/參加（組織或團體）】時，join後面沒有必要用介詞in.原題中，語境是：It's not necessary to 【join a health center 】to keep fit.爲了保持健康，沒有必要【加入健康中心】。這正符合join的第一種用法，所以，不需要用in。