一、动词ing形式作状语时的形式
[观察例句]
①They sat in the classroom，reading the books borrowed from the library.
②I stood there motionless，not knowing what to do.
③Having succeeded in the test，he became more confident.
④Not having finished his homework，the boy was still doing it in the classroom.
⑤Having been told several times，he still couldn't understand how to operate the machine.
