Final answer:
A) Hypochondriasis, also known as illness anxiety disorder, is a mental health condition characterized by a preoccupation with having a serious illness despite reassurances from medical professionals. Individuals with hypochondriasis often visit doctors frequently and experience excessive worry about their health.
Step-by-step explanation:
The mental health condition characterized by a preoccupation with having a serious illness despite reassurances from medical professionals, frequent doctor visits, and excessive worry about health is Hypochondriasis. This condition is also known as illness anxiety disorder. Individuals with hypochondriasis may constantly seek reassurance from healthcare providers, undergo numerous medical tests, and experience significant distress related to their health concerns.