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-- The math problem _________ is not difficult.

--- But after several tries , I have to give up _________ on it .

A．it’s , working      B．itself , to work      C．itself , working      D．its , to work

The math problem is too difficult ,I can’t__________ .

The math problem is so hard. I really don’t know     .

A. how to do it  B. how to do C. what to do it D. where to do it

The math problem is too difficult ,I can’t__________ .

A．work out it                            B．work it out

C．work them out                         D．put it out