Santa Clara island is home to a large. . .

[Vincen]

Santa Clara island is home to a large population of wild horses, but horses are not native to the island. It is known that Spanish settlers colonized Santa Clara island and lived there continuously from 1650 to 1740, and the bones of horses were recently found in an excavation site that can be dated to the early 1700s. Therefore it is likely that the Spanish settlers were the ones who introduced horses to Santa Clara island.

The answer to which of the following questions would be most useful in evaluating the validity of the conclusion drawn above?

A. Did the Spanish settlers introduce horses to any other islands near Santa Clara?
B. Have any excavations found evidence of human settlers who lived on Santa Clara prior to 1650?
C. Were any other nonnative species introduced to Santa Clara island by the Spanish settlers?
D. Have any human settlements remained on Santa Clara island since 1740?
E. Does Santa Clara island contain any horse bones that can be dated to before 1650?

The OA is E.

Wow. This CR question is really difficult. Should I answer each question and then think what is the most useful answer?

[DavidG@VeritasPrep]

Santa Clara island is home to a large population of wild horses, but horses are not native to the island. It is known that Spanish settlers colonized Santa Clara island and lived there continuously from 1650 to 1740, and the bones of horses were recently found in an excavation site that can be dated to the early 1700s. Therefore it is likely that the Spanish settlers were the ones who introduced horses to Santa Clara island.

The answer to which of the following questions would be most useful in evaluating the validity of the conclusion drawn above?

A. Did the Spanish settlers introduce horses to any other islands near Santa Clara?
B. Have any excavations found evidence of human settlers who lived on Santa Clara prior to 1650?
C. Were any other nonnative species introduced to Santa Clara island by the Spanish settlers?
D. Have any human settlements remained on Santa Clara island since 1740?
E. Does Santa Clara island contain any horse bones that can be dated to before 1650?

The OA is E.

Wow. This CR question is really difficult. Should I answer each question and then think what is the most useful answer?

Conclusion: Spanish settlers introduced horses to Santa Clara island.
Premises: Spanish settlers arrived in 1650, there continuously until 1740. Horse bones were found dating to early 1700's.

We want a question whose answer will shed definitive light on the conclusion, either that it was certainly the Spanish settlers who brought horses to the island or it wasn't. Moreover, he already have evidence that horses and Spanish settlers were present on the island together, so we're wondering, is it possible that the horses were already there when the settlers arrived in 1650?

This is what E tells us. If Santa Clara contains horse bones that date to before 1650, then it couldn't possible have been the Spanish setters who introduced the horses when these settlers didn't arrive until 1650.