请问这道题选什么?并说明原因.

题目

请问这道题选什么?并说明原因.
All passengers not going to London must changed trains at this stop.
A.not going B.aren't going C.don't go D.who not going

答案

All passengers not going to London must changed trains at this stop.这个句子的答案你选A对了.
以下我的解释请你耐心地看下去,以后,类似的题目,你都可以按我讲的这个思路去解.记住啊!很有用的哦!
如果选B或D的话,就是：
All passengers aren't going to London must changed trains at this stop.
All passengers don't go to London must changed trains at this stop.
这样的话,All passengers aren't going to London 和All passengers don't go to London 分别都够成一个句子,句子的谓语分别是aren't going、 don't go .那么后面的谓语must change（不是must change!）就没法解释了——它的主语是什么?
如果你要说谓语must change的主语是All passengers aren't going to London 和All passengers don't go to London 这两个句子的话,那就错了.原因在于在英语句子中,如果主语是句子——称为主语从句——的话,作主语的从句必须由连接词引导,而All passengers aren't going to London 和All passengers don't go to London 这两个句子的句首恰恰就没有连接词.所以,就不能选B或D,不可以让它们构成句子.所以动词也就只能是非谓语动词形式了.如此,四个答案中最符合的就只有A了——not going,用现在分词形式,因为not going表示的动作在意义上是主语 All passengers 做的.
另外,如果在not going to London前加上who are,它就是一个定语从句了.
至于D项为什么不能选,参照前面的解释,可知是因为它没有讲.