Look at sb doing sth不是现在进行词么?如果是怎么没有be动词啊?书上是This group of people playing...Look at sb doing sth不是现在进行词么?如果是怎么没有be动词啊?书上是This group of people playing beach volleyball

Look at sb doing sth不是现在进行词么?如果是怎么没有be动词啊?书上是This group of people playing...Look at sb doing sth不是现在进行词么?如果是怎么没有be动词啊?书上是This group of people playing beach volleyball
Look at sb doing sth不是现在进行词么?如果是怎么没有be动词啊?书上是This group of people playing...
Look at sb doing sth不是现在进行词么?如果是怎么没有be动词啊?书上是This group of people playing beach volleyball,都没be动词

Look at sb doing sth不是现在进行词么?如果是怎么没有be动词啊?书上是This group of people playing...Look at sb doing sth不是现在进行词么?如果是怎么没有be动词啊?书上是This group of people playing beach volleyball
at,of后面要接着名词,接动词则要名词化.
这就是动词的名词化,就是做名词用的动词,动词变名词就是+ing.
当然有时候意思中带有正在在做什么的意思.

不是的 因为 at 和 of都是介词 介词后面的动词都要用ing形式 不关BE动词的事