Kant argues that we should never use people as a means:
unless we are certain that doing so will lead to the greatest overall happiness.
unless we can do so without their knowledge.
unless they are guilty of breaking the law.
unless we are respecting their rational autonomy at the same time.

disorders of the brain include both behavior disorders and other psychiatric illnesses. the primary difference between a behavior disorder and another type of psychiatric disorder is the presence of choice. psychiatric conditions are considered to be involuntary while in behavior disorders, choices are essential.

the first question's answer is a.