Here we have a strengthen with necessary premise question. Remember that a premise is necessary for a conclusion if the falsity of the premise guarantees or brings about the falsity of the conclusion. First we check to see if the answer choice strengthens the passage, and then, if it does strengthen, we negate the answer choice to see if its negation makes the argument fall apart. If the answer choice does both those things then it is our correct answer.
The conclusion of the argument is: "the cause of increased deaths is the use of bronchial inhalers by asthma sufferers to relive their symptoms."
Why? Two explanations are offered: (1) recording of deaths due to asthma has become more widespread and accurate in the past decade than it had been previously; (2) an increase in urban pollution. But, we are told that the rate of deaths due to asthma has increased dramatically even in cities with long-standing, comprehensive medical records and with little or no urban pollution.
Answer choice (E) states: "Increased urban pollution, improved recording of asthma deaths, and the use of bronchial inhalers are the only possible explanations of the increased death rate due to asthma."
Does this strengthen? Yes. If the above three are the only possible explanations of increased death rate due to asthma, and we know that the first two are not present, then it strengthens the conclusion that the third explanation is the cause of the deaths.
We would write it: "If death rate increases, then it's either urban pollution, or improved recording, or the use of bronchial inhalers."
(E) DI ==> UP or IR or BI not UP and not IR and not BI ==> not DI
We know we have "DI," so we will have at least one of "UP," "IR" or "BI." We know that in certain cities we do not have "UP" and we do not have "IR," so if (E) were true, then we must have "BI."
Does the negation of answer choice (E) make the argument fall apart? Yes.
Negation: Increased urban pollution, improved recording of asthma deaths, and the use of bronchial inhalers are not the only possible explanations of the increased death rate due to asthma.
Well, if these are not the only explanations, then there could be some other reason as to why the death rate is increasing that is not due to the use of bronchial inhalers.
Thus, answer choice (E) is the correct answer because the argument depends on it.
Hope that clears things up! Please let us know if you have any other questions.
Ro13July 22, 2018
So does D weaken because it states that it aggravates other diseases?
MehranJuly 23, 2018
Hi @Ro13, thanks for your post. In this question, you are asked to strengthen a conclusion that states that the use of bronchial inhalers is the cause for increased asthma death rates, NOT urban pollution or improved recording. Importantly, the only support provided for this conclusion in the stimulus is that "the rate of deaths due to asthma has increased dramatically even in cities with long-standing, comprehensive medical records and with little or no urban pollution."
Answer choice (D) does not strengthen this argument; it, as you note, introduces another possible cause (the aggravation of other diseases). Introducing another possible cause is a way to *weaken* a cause and effect argument (the other two ways are (1) to show the cause may exist without the effect, and (2) to show the effect exists without the cause). Because answer choice (D) weakens the argument, it is incorrect on this Strengthen with Necessary Premise question.
Hope this helps! Please let us know if you have any additional questions.
