Cognitive-behavioral techniques: a. may substitute for drug treatments in case of severe hypertension. b. can be used without supervision and have no side effects. c. are expensive and highly difficult to implement. d. have been moderately successful in the treatment of hypertension.

C.  can be used without supervision and have no side effects

Explanation:

Cognitive behavior therapy is a type of approach in behavior modification where the therapist/doctor looks at other factors that may affect the well-being of that person; finding goals to help change their behaviors.  

In this case; what is causing the hypertension and what they can do to counter that "problem" without drugs.