Final answer:
Doctors and pharmacists are reliable sources for medical information due to their professional healthcare training, while mechanics, who are not medical experts, are not.
Step-by-step explanation:
When seeking reliable information on medical topics, one should look for expertise in the medical field. Among the options provided, a doctor and a pharmacist are professional healthcare providers with extensive training in medicine and pharmacology, respectively, making them reliable sources for medical information.
While engineers may work in related fields, such as bioengineering, developing medical devices or health management systems, they do not necessarily have the medical degree required to provide medical advice. Similarly, mechanics focus on machines and not on the human body, so they are not suitable sources for medical information.
It is crucial to evaluate the source's background, relevance to the medical field, and whether the information is based on peer-reviewed research to ensure reliability.