His “subject” is only running around with me.&run around with them英语书中有一句His “subject” is only running around with me（他的“课程”只是在我周围乱跑.）而书中又有一句run around with them（与他们一起在周围跑）为什么一句“run”变“running”而另一句没变.再问一下brush one’s teeth中one’s代表/意为什么还有after running中的“run”为何也用“running”
问题描述：
His “subject” is only running around with me.&run around with them
英语书中有一句His “subject” is only running around with me（他的“课程”只是在我周围乱跑.）而书中又有一句run around with them（与他们一起在周围跑）为什么一句“run”变“running”而另一句没变.
再问一下brush one’s teeth中one’s代表/意为什么还有after running中的“run”为何也用“running”
答
前面一句结构：be running
后面一句：run
答
running与前面的is构成be+doing 形式,有正在干什么的意思；如果去掉系动词be,run就承担谓语,所以不用动名形式.
brush one’s teeth中的one’s泛指某个主体,可直译为刷牙.