GMAT Question of the week
Increased atmospheric concentrations of carbon dioxide (CO2)
) in the atmosphere can have a fertilizing effect on certain crops, provided that it is possible for farmers to provide adequate water and fertilizer for the plants to grow more quickly. For this reason, many non-scientists have long held that increases in global atmospheric carbon dioxide will also lead to increased agricultural production, offsetting any shortages due to shifting water availability and increased temperature. This in turn, these individuals argue, will lead to decreased global malnutrition and undernutrition as the increased supply of food drives down its cost.
However, research on the nutritional content of crops grown at Free Air (CO2)
Enrichment - or FACE - sites suggests that while crops may grow more quickly in elevated concentrations of carbon dioxide, increased growth comes at a price. Crops grown in elevated levels of carbon dioxide have lower levels of protein and of micronutrients such as zinc. Since the world’s population gets the majority of its protein and other micronutrients from plant-based sources, such a shift could have dire consequences. Scientists estimate that by 2050 an additional 175 million people could become zinc deficient, and an additional 120 million could become protein deficient as the nutritional content of staple crops falls between 5 and 17 percent.
Which of the following can be inferred from the passage?
D) There are currently some people who are considered to have a zinc deficiency.
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.