Final answer:
Social isolation (C) is a common problem during middle adulthood as adults face changes such as children leaving home and retirement, leading to less social interaction.
Step-by-step explanation:
A common problem during middle adulthood, which lasts from about the mid-30s to the mid-60s, is social isolation (C). During this stage, adults often focus on raising families and achieving career goals, and as their children grow up and leave home, the risk of social isolation can increase. Additionally, as people age, they may also face retirement, which can lead to less social contact and feelings of loneliness.
The challenges of middle adulthood often include developing chronic diseases such as type 2 diabetes, cardiovascular disease, or cancer. While these are serious health concerns, the element of social isolation specifically addresses the psychological and social aspects of middle adulthood rather than the physiological changes. While job loss (D) can happen during this phase, it is not identified as a common issue directly associated with middle adulthood.