When diagramming it's important to identify the conclusion. Here the conclusion is that
Quote:
the metallurgical techniques used to make the rings found in Mexico were learned by Mexican artisans from Ecuadorian counterparts.
The premises are that
(1) Metal rings recently excavated from seventh century settlements in the western pat of Mexico were made using the same metallurgical techniques as those used by Ecuadorian artisans before and during that period
(2) These techniques are sufficiently complex to make their independent development in both areas unlikely
(3) the people of these two areas were in cultural contact
The question is asking what information would be most useful in order to evaluate the argument. In other words, the question is asking you to identify the piece of information that would be most helpful, or most damaging, to the argument.
Let's think about (C) - "Whether artisans from western Mexico could have learned complex metallurgical
techniques from their Ecuadorian counterparts without actually leaving western Mexico".
Suppose that you find out that YES, the Mexicans
could have learned from the Ecuadorans without leaving Mexico. So what? "Could have" doesn't mean that they did or did not. And anyway, the conclusion is about whether the Mexicans learned from the Ecuadorans, not whether they did so
without leaving Mexico
Suppose you find out that NO, the Mexicans could
not have learned from the Ecuadorans without leaving Mexico. So what? Maybe they learned from the Ecuadorans by traveling to Ecuador.
Thus, the information discussed in (C) is of little use in assessing the argument.
On the other hand, the information in (A) is useful. If you find out that YES, these objects were traded from Ecuador to Mexico, the argument is thereby strengthened. The new piece of information plugs a kind of hole in the argument - the vague reference to "cultural contact" does not make clear whether there was any exchange of metal goods or metallurgical information.
-Jad