I ultimately chose (C) but was rather uncomfortable trying to eliminate (D). It seems to me they are conceptually similar:
(C) provides a reason to think there was no "deception" involved - Dr. Faris wasn't deceiving, he knew that improved sleep would likely result from the med.
(D) also provides a reason to think there was no "deception" involved - with other doctors prescribing this medication to patients who had trouble sleeping, Dr. Faris was less likely to be "deceiving" and more likely to be simply going along with the typical prescriptions he/she has observed from other doctors treating patients who had trouble sleeping.
I recognize (D) is more of a stretch, which is why I chose (C), but I'm rarely this uncomfortable on a LR question so early in a section, and would love any further insight on how to more confidently dispatch (D).
Thanks in advance!
Admin Note: Edited title. Please use the format: "PT#.S#.Q# - brief description of the question"