Hi
SonalSinha803 ,
Here is the thing. No one in the world can answer you this question except GMAC themselves.
As far as I know, leaving a question answered may lead to varying negative marking.
Logically, I am doing very good and I encounter a question of 700+ level and I miss answering it, I may have more negative marking than if I would have left a question of low difficulty level.
Again, this is my assumption and I might be wrong.
Please note that it is strictly not recommended to leave any question answered.
All the best