Sandeep190789

Hello Everyone, I have started my GRE preparation just two days back. I came across a sentence completion question which contains a following sub sentence. " Not because there are doubts about its authenticity or even great reservations to its price. " according to me this sentence tells us about something whose authenticity is doubtful and have high price. I read the explanation of this sentence that is quiet opposite to what I thought, according to explanation the thing is authentic and cheap. can you please explain what effect not because has caused here. Thanks in advance