Mountain goats in a particular region who climb to the highest altitudes to acquire plants to eat are less susceptible to disease than those who don’t climb as high. It has been hypothesized that eating certain plants that are only available at the higher altitudes has boosted the goats’ immune system.

Which of the following, if true, most seriously weakens the hypothesis about certain being goats less susceptible to disease?

(A) It has been shown that the goats that don’t climb as high still benefit from eating the plants that are only available at the higher altitude.
(B) Goats that climb to the higher altitudes sometimes suffer from respiratory illness.
(C) Eating too much of the plants that are found at the higher altitude is not beneficial to the goats.
(D) Goats with stronger immune systems are able to climb higher.
(E) Some goats with average immune system strength attempt to climb to higher altitudes.


OA D

Source: EMPOWERgmat