It is apart of cellular DNA an ATP, and is a major component of bones and teeth, it is often only available in limited quantities in the the environment.
The answer is option B "psychiatrist." Psychiatrist are specialized in medicine and on finding cures for common diseases which would make them doctors. Also its not option A because a <span> psychologist is a person who studies in behaviors which is a therapist, its not option C because a social worker works mainly in families but not for the health. Its also not option D because a case manager who is placed to render court cases.
Hope this helps!</span>