All we can do is look at mug shots.这句话的句子成分怎么分析?

问题描述:

All we can do is look at mug shots.这句话的句子成分怎么分析?
all we can do 是个什么成分?是主语从句?那连接词呢,到哪里去了?这个结构是特殊的结构吗?

All (that )we can do 是主语从句,that 可省略.all that =what 可以改写 what we can do ,可以作为一个固定的表达记住它!
All sb can do is ...
For example:All I can do is wait
All she can do is stay at home watching tv.