请教英语语法,Now read how she felt after being in the hiding place since July 1942.Now read how she felt after being in the hiding place since July 1942.请问after后面为什么不是"she had been ",而是用"being"?这个语法是独立主格吗?

问题描述:

请教英语语法,Now read how she felt after being in the hiding place since July 1942.
Now read how she felt after being in the hiding place since July 1942.请问after后面为什么不是"she had been ",而是用"being"?这个语法是独立主格吗?