Physician: The hormone melatonin has shown promise as a

Melatonin
 
Step 1: Identify the Question

The word flawed in the question stem indicates that this is a Find the Flaw question. Flaw questions are closely related to Weaken questions with one big difference: Weaken questions will contain the language if true, while Flaw questions will NOT.

Step 2: Deconstruct the Argument

Dr: M = effective, BUT: side effects unknown → can’t prescribe
Pa: you prescribe other meds w/ side effects → why not M?

The physician’s argument is this: M’s side effects are unknown, so he can’t recommend using it. The patient counters this argument by claiming that the physician must actually have some other reason to avoid prescribing M. The physician prescribes other medications that have serious side effects, so unknown side effects aren’t (according to the patient) a valid excuse.

Step 3: Pause and State the Goal

On Flaw questions, the goal is to find an answer choice that undermines one of the argument’s assumptions. What is the patient overlooking or what bad assumption is he making in drawing his conclusion?.

Step 4: Work from Wrong to Right

(A) Unless the argument also provides information about natural melatonin, knowing that the two types of melatonin are different from each other doesn’t affect the argument, which is purely about synthetic melatonin.
(B) This answer choice states that there is another reason that the physician chooses not to prescribe melatonin—he is concerned about its efficacy, rather than its safety. However, this isn’t something that the patient has failed to consider. In fact, this type of issue is exactly what the patient is concerned about.
(C) Failing to consider the serious medical consequences of sleep disorders is a criticism that would be more appropriately levied at the physician than the patient.
(D) The argument deals only with which side effects a medication has, not the time frame in which those side effects make themselves known.
(E) CORRECT. The doctor’s argument specifically regards the unknown side effects of melatonin. In the patient’s response, he draws an analogy between melatonin and other medications with known serious side effects. In doing so, the patient assumes—perhaps incorrectly—that known and unknown side effects should be treated in the same way.