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#40960
Complete Question Explanation
Must Be True, SN. The correct answer choice is (B)
The stimulus contains a fact set and features conditional reasoning, which is identifiable by the use of the necessary condition indicator “unless” in the first sentence. Applying the Unless Equation, the phrase modified by “unless” becomes the necessary condition, whereas the remainder is negated and becomes the sufficient condition. However, you should notice the sufficient condition indicator “any” modifying the clause “antibiotics used against the bacteria,” which needs to be factored into the relationship.
Thus, if the bacterial species does not become resistant to the antibiotics used against it, then either the antibiotics did not completely eliminate the bacterial species, or no antibiotics were used against it:
In the contrapositive form, if any antibiotic is used against the bacterial species and that antibiotic does not completely eliminate it, the bacterial species will develop greater resistance to that antibiotic. Some students would prefer to diagram the contrapositive first, since the “unless” modifier is logically equivalent to the phrase “if not.”
The second premise tells us that no single antibiotic now on the market is powerful enough to eliminate bacterial species x:
Therefore, we can use the contrapositive of the conditional relationship in the first premise to prephrase the conclusion that if any antibiotic is used against bacterial species x, the species will become more resistant to it (since the other sufficient condition has already been established):
This prephrase is tremendously helpful in attacking the answer choices and immediately proves that answer choice (B) is correct. Because stimuli containing conditional reasoning in combination with Must Be True questions frequently produce contrapositive answer choices, you should apply the contrapositive and prephrase an answer choice based on the contrapositive.
Answer choice (A): On the basis of the evidence presented in the stimulus, we cannot estimate the likelihood that an antibiotic can be developed to eliminate bacterial species x. Although no single antibiotic now on the market is powerful enough to eliminate bacterial species x completely, it is impossible to predict what can happen in the future.
Answer choice (B): This is the correct answer choice, which predictably contains the contrapositive of the first sentence of the stimulus: because no single antibiotic now on the market is powerful enough to eliminate bacterial species x, any antibiotic used against the bacterial species will become more resistant to it.
Answer choice (C): At first glance, this may seem like an attractive answer. If no single antibiotic now on the market is powerful enough to eliminate bacterial species x completely, is it not likely that the only way of completely eliminating bacterial species x is by combining two or more antibiotics? Unfortunately, we are looking for an answer that Must Be True, not just likely to be true. There is always the possibility that there are other ways to completely eliminate bacterial species x (take across-the-board mandatory immunizations, for instance). Because we have no information as to whether there are other ways to eliminate the bacterial species in question, this answer choice cannot be proven by the stimulus and is therefore incorrect.
Answer choice (D): Although no single antibiotic is powerful enough to eliminate the bacterial species x, perhaps there are other ways to eliminate it (vaccinations, a combination of several different antibiotics, etc.). Even if those ways did not work, it would still be unreasonable to conclude that the bacterial species in question will inevitably become more virulent. The topic of virulence was never discussed in the stimulus, and therefore cannot be proven by the information in it.
Answer choice (E): This appears to be an attractive answer because we do know that a bacterial species will inevitably develop greater resistance within a few years to any antibiotics used against it, unless those antibiotics can completely eliminate it. Clearly, no antibiotic on the market can completely eliminate bacterial species x. However, we cannot be 100% certain that the bacteria today is more resistant to some of the antibiotics that have been used against it in the past, because we do not know when (or whether) these antibiotics were actually used. The author clearly states that it takes a few years for the bacterial species to develop greater resistance to any antibiotic that fails to completely eliminate it. Therefore, if the ineffective antibiotics were used only a few months ago, we cannot expect that the bacteria are more resistant to them today than it was before they were used.
Must Be True, SN. The correct answer choice is (B)
The stimulus contains a fact set and features conditional reasoning, which is identifiable by the use of the necessary condition indicator “unless” in the first sentence. Applying the Unless Equation, the phrase modified by “unless” becomes the necessary condition, whereas the remainder is negated and becomes the sufficient condition. However, you should notice the sufficient condition indicator “any” modifying the clause “antibiotics used against the bacteria,” which needs to be factored into the relationship.
Thus, if the bacterial species does not become resistant to the antibiotics used against it, then either the antibiotics did not completely eliminate the bacterial species, or no antibiotics were used against it:
In the contrapositive form, if any antibiotic is used against the bacterial species and that antibiotic does not completely eliminate it, the bacterial species will develop greater resistance to that antibiotic. Some students would prefer to diagram the contrapositive first, since the “unless” modifier is logically equivalent to the phrase “if not.”
The second premise tells us that no single antibiotic now on the market is powerful enough to eliminate bacterial species x:
Therefore, we can use the contrapositive of the conditional relationship in the first premise to prephrase the conclusion that if any antibiotic is used against bacterial species x, the species will become more resistant to it (since the other sufficient condition has already been established):
This prephrase is tremendously helpful in attacking the answer choices and immediately proves that answer choice (B) is correct. Because stimuli containing conditional reasoning in combination with Must Be True questions frequently produce contrapositive answer choices, you should apply the contrapositive and prephrase an answer choice based on the contrapositive.
Answer choice (A): On the basis of the evidence presented in the stimulus, we cannot estimate the likelihood that an antibiotic can be developed to eliminate bacterial species x. Although no single antibiotic now on the market is powerful enough to eliminate bacterial species x completely, it is impossible to predict what can happen in the future.
Answer choice (B): This is the correct answer choice, which predictably contains the contrapositive of the first sentence of the stimulus: because no single antibiotic now on the market is powerful enough to eliminate bacterial species x, any antibiotic used against the bacterial species will become more resistant to it.
Answer choice (C): At first glance, this may seem like an attractive answer. If no single antibiotic now on the market is powerful enough to eliminate bacterial species x completely, is it not likely that the only way of completely eliminating bacterial species x is by combining two or more antibiotics? Unfortunately, we are looking for an answer that Must Be True, not just likely to be true. There is always the possibility that there are other ways to completely eliminate bacterial species x (take across-the-board mandatory immunizations, for instance). Because we have no information as to whether there are other ways to eliminate the bacterial species in question, this answer choice cannot be proven by the stimulus and is therefore incorrect.
Answer choice (D): Although no single antibiotic is powerful enough to eliminate the bacterial species x, perhaps there are other ways to eliminate it (vaccinations, a combination of several different antibiotics, etc.). Even if those ways did not work, it would still be unreasonable to conclude that the bacterial species in question will inevitably become more virulent. The topic of virulence was never discussed in the stimulus, and therefore cannot be proven by the information in it.
Answer choice (E): This appears to be an attractive answer because we do know that a bacterial species will inevitably develop greater resistance within a few years to any antibiotics used against it, unless those antibiotics can completely eliminate it. Clearly, no antibiotic on the market can completely eliminate bacterial species x. However, we cannot be 100% certain that the bacteria today is more resistant to some of the antibiotics that have been used against it in the past, because we do not know when (or whether) these antibiotics were actually used. The author clearly states that it takes a few years for the bacterial species to develop greater resistance to any antibiotic that fails to completely eliminate it. Therefore, if the ineffective antibiotics were used only a few months ago, we cannot expect that the bacteria are more resistant to them today than it was before they were used.
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Species Eliminate Completely