Answer:
Option A, a medication with the potential to become habit forming or to be abused
Explanation:
Controlled substances are not just illicit (or illegal) drugs but also medications that can be prescribed by healthcare providers, thus ruling out option B. These medications are often administered in the in-patient setting (e.g. oxycodone for pain) as well as to some patients for take-home purposes, ruling out option D. Lastly, most, if not all, medications are made from potentially dangerous substances -- the phrase "the dose makes the poison" applies to medicine in a quite literal manner; something as seemingly innocuous as Tylenol (acetaminophen) or Nyquil (acetaminophen, dextromethorphan, and doxylamine) can be dangerous if taken in excess. Thus, option C is also out.
Controlled substances are any drugs (traditional or recreational/illicit) that can be habit-forming or have the potential to be misused and abused by the patient, option A.
The DEA categorizes these drugs into certain classes, called schedules, based on this abuse potential. Schedule 1 medications are those described in option B. The other schedules (2 through 5), however, can be prescribed but their risks must be emphasized in the patient education and these patients may need to be closely monitored, assessed, and reassessed for the duration of their pharmacotherapy.
