Which of the following most logically completes the argument?
A new machine for harvesting corn will allow rows to be planted only fifteen inches apart, instead of the usual thirty inches. Corn planted this closely will produce lower yields per plant. Nevertheless, the new machine will allow corn growers to double their profits per acre because ________.
- with the closer spacing of the rows, the growing corn plants will quickly form a dense canopy of leaves, which will, by shading the ground, minimize the need for costly weed control and irrigation
- with the closer spacing of the rows, corn plants will be forced to grow taller because of increased competition for sunlight from neighboring corn plants
- with the larger number of plants growing per acre, more fertilizer will be required
- with the spacing between rows cut by half, the number of plants grown per acre will almost double
- with the closer spacing of the rows, the acreage on which corn is planted will be utilized much more intensively than it was before, requiring more frequent fallow years in which corn fields are left unplanted
Answer & Explanation
Correct answer is (A).
When creating GMAT critical reasoning questions, test writers know exactly what you will be thinking about when certain scenarios are developed, and they deviously use your own mind against you. You must learn to fight this natural instinct: always question the first thing you think about in a critical reasoning question…it is usually a trap! Just as the positive/negative number properties were used to distract you in the DS sample question covered here, so the “obvious” answer plays the same role here.
Most people immediately gravitate to (D) in this question (you are looking for a premise that improves the quality of the conclusion): if farmers are able to plant twice as much corn because they have reduced the width between rows, then that would explain how they can make a lot more profit. Answer choice (D) seems perfect and most people pick it: “with the spacing between rows cut by half, the number of plants grown per acre will almost double.”
However, in critical reasoning you must learn to be extremely particular with the given conclusion. The conclusion in this stimulus is the following: “the new machine will allow corn growers to double their profits per acre.” Yet, you are also given an important fact in the argument that will qualify the statement in (D): “Corn planted this closely will produce lower yields per plant.” If you plant twice as much corn but you know for a fact that the closer rows will mean a lower yield per plant, then it is impossible to double profits from twice as many plants in closer rows. Additionally, the answer in (D) states “almost double,” which makes it even weaker. You want the answer to be (D) because that is what your mind anticipates, but numerous elements make it conclusively incorrect. It is really not telling you anything new and it does not at all explain how the farmers can still double profits even if yields are lower per plant.
The correct answer (A) is not expected nor particularly satisfying, but it is the only one that works. If the need for costly weed control is lessened by the narrow rows, then the combination of more corn and lower expenses can explain how profits would be doubled by farmers even with lower yields per plant. Remember that profits involve two components: revenue, which in this argument cannot explain the doubling of profits by itself, and costs, which if reduced along with increased revenue from more corn can explain a doubling of profit even with reduced yields. With practice, you will learn to be very suspicious about your first reaction when reading GMAT critical reasoning questions.
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