Scurvy is caused by the deficiency of which vitamin

Which of these gives the best indication that a health service is based on pseudoscience? a. the service is not controversial and is supervised by medical professionals. b. the service has been extensively researched,has a high success rate,and is expensive c. the service is inexpensive, is based on research, and has been around for a long time d. the service has not been researched and is expensive