Look-at-this-group-of-people-playing-on-the-beach.语法有误吧?be呢?

题目

Look-at-this-group-of-people-playing-on-the-beach.语法有误吧?be呢?
不过这是教科书上的,

答案

这是一个祈使句
后边的playing on the beach 是做定语
修饰people的
句中已经有了谓语动词look了 就不能再出现第二个谓语动词
原句应该是look at this group of people who is playing on the beach
省略了而已