Final answer:
A 45-year-old is in the stage of middle adulthood, characterized by career progression, physical signs of aging like wrinkles and gray hair, and an increased risk of health issues like heart disease and diabetes.
Step-by-step explanation:
A person who is 45 years of age is in the stage of middle adulthood. This period spans from approximately the mid-30s to the mid-60s. During middle adulthood, many individuals focus on achieving career goals, and it's common for their children to grow up and leave home. Physically, signs of aging become more evident, such as the development of wrinkles and graying hair. Additionally, the risk of health problems increases during this time, with conditions like heart disease, cancer, and type 2 diabetes becoming more prevalent.