Thanks for the question! So let’s take a look at the stimulus first. We’re told that asthma death rates have doubled, with two possible explanations. But the author doesn’t think either of those explanations are satisfactory, and so the author concludes instead that the cause of increased death has to do with the use of bronchial inhalers to relieve symptoms.
Now we’re asked for a necessary assumption in this argument. Let’s take a look at (D) and think: is this absolutely necessary for the argument? If we negate it and the argument still stands, then it’s not necessary, and we can eliminate it. Let’s say that the use of bronchial inhalers doesn’t aggravate these other diseases that frequently occur among other asthma sufferers. Is it still possible that the bronchial inhalers are the cause of increased deaths? Absolutely! And so (D) can’t be a necessary assumption. Also, notice that we’re talking about an increase in the death rate of asthma, so introducing considerations of fatal outcomes that aren’t asthma-related isn’t relevant here. We’re looking at death by asthma, not deaths of people with asthma, and there’s a difference between the two.
Hope this helps! Feel free to ask any other questions that you might have.
