同学你好，该知识点来自沪江网校《英语零基础直达大学六级3年随心畅学班【老学员专享】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
如果问题较多，请分开提问。

1. 答案应该是policemen和policewomen，都用复数形式
2. be on a trip 在旅途中，主语是：介词in, out of, with, except, besides, without, as well as, no less than, rather than, more than, but, along with, together with, like, including, in addition to等所连接的两个名词时，谓语动词的形式应与这些词前面的名词的数保持一致。如：
(1) At the meeting, one in four is against the decision. 会上由四分之一的人反对这一决议。
(2) The teacher with his students is discussing a question. 老师和学生们在讨论问题。
3. 他们是工程师，不止一个工程师，用复数形式。
4. 使役动词let，make，have等，感官动词see，hear，feel，watch，notice，look at，listen to等，后常跟不带to的不定式作宾语补足语。例如：
A woman saw it happen when she was walking past. 一位妇女路过时看到了。
We often heard her sing in the next room. 我们经常听到她在隔壁唱歌。
注意：在被动语态句子中，不定式前必须加to.例如：
He was made to do it. 他被迫做这件事。
She was often heard to sing in the next room. 经常听到她在隔壁唱歌。
5. Cathy和她的哥哥，两个人，而且主语是these，应该用are
6. 是一个电视还是电脑，在两者中作选择，or

祝同学学习进步~