专题:
be a member of / be in ...延续性动词又名持续性动词，它表示能够延续的动作，这种动作可以长时间延续下去或产生持久的影响。动词按其动作发生的方式、动作发生过程的长短，可分为延续性动词和终止性动词。
join相关例句
It costs £ 20 to join.
需交20英镑才可参加。
People of various party allegiances joined the campaign.
各个不同政党的拥护者都参加了这次活动。
Join a social club to make new friends.
加入一个社交俱乐部，好交一些新朋友。
We'll join up with the other groups later.
我们以后再与其他小组会合。
Over the past year, the company has joined the big league.
去年一年中，公司已跻身一流之列。
延续性动词
延续性动词能够延续的动作。如：study, work, stand, lie, know, walk, keep, live,have, wait, watch, sing, read, sleep,stay等。
1、 He worked all day in the laboratory. 他在实验室干了一天。
2、I waited for you for more than half an hour. 我等你等了半个多小时了。
表示时间段的短语有:for+ 时间,for 2 years; since从句,since he came here; since+时间点名词,since last year, since 5 days ago; how long; for a long time等。