To win his action in negligence against a professional person, the plaintiff must prove, among other things, that the defendant's conduct was below an acceptable standard of care. Which of the following is the legal standard of care demanded of a professional person?

A) That he act to the very best of his ability

B) That he act sincerely and with goodwill

C) That he act as may reasonably be expected of the normally skilled professional of that type

D) That he act sincerely and as may reasonably be expected of a skilled professional

E) That he act as a reasonably prudent person