Advertisement: At most jewelry stores, the person assessing the diamond is the person selling it so you can see why an assessor might say that a diamond is of higher quality than it really is. But because all diamonds sold at Gem World are certified in writing, you’re assured of a fair price when purchasing a diamond from Gem World.

The reasoning in the advertisement would be most strengthened if which one of the following were true?

a) Many jewelry stores other than Gem World also provide written certification of the quality of their diamonds.
b) The certifications of diamonds at Gem World are written by people with years of experience in appraising gems.
c) The diamonds sold at Gem World are generally of higher quality than those sold at other jewelry stores.
d) The diamond market is so volatile that prices of the most expensive diamonds can change by hundreds of dollars from one day to the next.
e) The written certifications of diamonds at Gem World are provided by an independent company of gem specialists.

I have picked this question from the link http://gmatclub.com/forum/advertisement-at-most-jewelry-stores-the-person-assessing-136423.html .
I am not able to understand the answer provided for this question.

I picked out my answer on the following lines.

The Main Issue that the argument is trying to address is

Whether assessor or the seller have to be the same person in Gem World ?


Options A, C, and D were irrelevant to the main issue.

I am confused which one to choose, B or E. I eventually picked B, which stands incorrect.

Can I get a proper explanation for the answer choice B and E.

Thanks,

Ankit Gupta