what is done can't be undone

问题描述:

what is done can't be undone
还有what she needs to study hard.这两句话what是做is done的主语,和she needs的宾语吗?what相当与定语从句the thing that吗?

what she needs is to study hard吧少了个is吧
恩 2个理解都正确 可以这么说