Critical Reasoning

Numismatist: In medieval Spain, most gold coins were minted from gold mined in West Africa, in the area that is now Senegal. The gold mined in this region was the purest known. Its gold content of 92 percent allowed coins to be minted without refining the gold, and indeed coins minted from this source of gold can be recognized because they have that gold content. The mints could refine gold and produced other kinds of coins that had much purer gold content, but the Senegalese gold was never refined.
As a preliminary to negotiating prices, merchants selling goods often specified that payment should be in coins minted from Senegales gold.
Which one of the following, if true, most helps to explain this preference?

(A) because refined gold varied considerable in purity, specifying a price as a number of regined gold coins did not fix the quantity of gold received in payment.
(B) During this period most day-to day trading was conducted using silver coins, though gold coins were used for costly transactions and lost-distance commerce.
(C) The mints were able to determine the purity, and hence, the value, of gold coins by measuring their density.
(D) Since gold coins' monetary value rested on the gold they contained, payments were frequently made using coins.
(E) Merchants obtaining gold to resell for use in jewelry could not sell the metal unless it was first refined.

Could someone explain pls??

Is the answer A?

The paragraph highlights that gold sourced from Senegal was so pure (92% gold content to be precise), that it did not have to undergo a refinement process before coins were minted from it. On the other hand gold from other sources could be used to mint coins of even higher purity, but such gold needed to undergo a refinement process first. However, traders still preferred payment in terms of coins made from Gold in Senegal

B - Out of context. We are comparing gold coins made from Senegalese gold and other gold. Hence trading in silver coins is out of context
E - This would give reason to the merchants to trade in "other gold" which had already undergone refinement instead of Senegalese gold. Hence eliminate
D - Again we are not comparing why coins from Senegalese gold was preffered over coins from "other gold". Hence irrelevant
C - Density is irrelevant to the argument
A - Clearly explains that even though "other gold" underwent purification or refinement...the process wasn't standardised and hence the merchants could not ascertain how much gold they received if they specified the payment in terms of number of gold coind

Hence A....OA please?

One more for A.

B, C and D are out of scope.

E can be interpreted both "for" and "against" - inconclusive.

OA is A

I totally agree with answer A.