Increased atmospheric concentrations of carbon dioxide (CO2 )

OE Question 2

This specific question requires that you first understand what nonscientists are arguing and then that you look beyond that information to understand the flaw in that argument. Since the question asks about the nonscientists mentioned in paragraph 1, it's helpful to first think about what those nonscientists believe. Paragraph 1 states that they believe that because increased atmospheric CO2
can have a fertilizing effect on crops, that rising levels of CO2
will increase production in crops preventing food shortages and decreasing malnutrition.

To understand what the author thinks those people fail to consider, you then need to look at the next paragraph. (The word "however" at the beginning of that paragraph is a great indication of a shift occurring.) The next two sentences state that faster growth comes at the cost of nutritional content. This best matches answer choice (B): these nonscientists don't take into account that there might be phenomena that prevent this increased growth from actually affecting malnutrition.

Among the other answers, (A) can be eliminated because the ratio of edible to nonedible material isn't discussed, and (C) can be eliminated because distribution isn't discussed. (D) can also be eliminated because it is too specific: the author doesn't directly make any claims about water availability's effects, and (E) can be eliminated because there is no claim made that these two growth rates would differ.


OE Question 3

For this question, you should go straight to the answer choices, looking for the proposed inference that is guaranteed to be true based on the information provided in the text.

Choice (A) can be eliminated because the author doesn't give enough support to justify this inference. While it is possible that the number of people with a zinc deficiency wouldn't increase, it's also just as possible that a country could have a population boom, leading to famine and therefore more people with zinc deficiency. Both of these scenarios are allowed by the text.

Choice (B) can be eliminated as well since it runs counter to the information provided. While it's certainly possible, there is no evidence that crops will do anything other than what is described in the text.

Choice (C) is close, but isn't guaranteed. The passage says that increased yields will occur "provided" that farmers can get enough water and nutrients to plants, but doesn't state one way or the other whether this is actually possible.

Choice (D) is correct. The author states that "an additional" 175 million people could become zinc deficient, making it possible to infer that at least a few people worldwide are currently zinc deficient.

Choice (E) can be eliminated because you are told that the majority of micronutrients come from plant sources, but the word "majority" doesn't rule out the existence of alternative sources.