What does the sentence mean?
The argument above is open to the objection it makes the questionable assumption that...
It's a part of a question from GMAT. But I don't get it.

Question

What does the sentence mean?
The argument above is open to the objection it makes the questionable assumption that... 
It's a part of a question from GMAT. But I don't get it.

Answer

Could you post the entire sentence?

Answer

Hi Emie,

A 'questionable assumption' is an assumption that can be easily doubted or challenged.
It means that the argument above can be criticised because it makes an assumption that may well be wrong.

I hope that helps!
Ashley