This is an explanation question. The information in the passage suggests that genetic evidence links ancient chickens from the Americas to Polynesian chickens, and also to chickens in Europe and Asia. We're looking for a choice that explains why the genetic signature for the ancient and Polynesian chickens is the same as that of the European and Asian chickens.

(A) This is correct. If explorers took chickens that were related to the ancient chickens from the Americas, then bred them in Europe, it would explain the presence of the same genetic signature.
(B) The use of the chickens is completely off-topic.
(C) This is a general statement that doesn't explain or contradict the studies in the passage. Usually, such general statements are incorrect.
(D) This choice suggests that chickens similar to Polynesian chickens may been in Asia for some time, but the words "may be" make the choice much weaker.
(E) The study suggests that chickens first appeared in the Americas because they were introduced by someone other than the Spanish. If that ‘s the case, it doesn't matter when the Spaniards introduced chickens to the Americas.