There are 1.3 billion cows worldwide, and this population is growing to keep pace with the demand for meat and milk. ...

SamA on September 18, 2019

Hello @farnoushsalimian,

First, I will discuss why A is the correct answer. In the passage, we are given one benefit of better-quality diets: it causes the cows to produce less methane. This is the basis for the conclusion that methane pollution can be kept in check if cows are fed better food.

We are tasked with finding support for this argument. Answer choice A gives us the support that we need. The fact that better fed cows produce more meat and milk, means that fewer cows will be necessary, and the population won't have to grow quite so much. This means there are now two benefits the the higher-quality diets: fewer cows, and less methane per cow. This makes the author's conclusion stronger.

B is incorrect, because it seems to be at odds with the facts given in the passage. We already know that a better-quality diet leads to less methane, why do we care what elements are present in all types of cow feed? We don't know if the presence of methane's base elements even has an effect on actual methane released, so this answer choice doesn't support the conclusion.