Final answer:
A middle-aged individual with a stable job and family life is likely to show the most stable personality over the span of a year, due to fewer life changes and greater stability in social roles and daily routines compared to teenagers, young adults, and elderly retirees.
Step-by-step explanation:
The individual likely to show the most stable personality if measured today and again one year later is d) A middle-aged person with a stable job and family life. Personality stability tends to increase with age and life stability. The other individuals mentioned are at stages of life that are characterized by change. A teenager is going through puberty and facing identity formation challenges, while a young adult in a new job is likely adapting to significant career changes. An elderly person in retirement may also face changes in health, social roles, and activity levels which can impact personality stability to some degree. However, a middle-aged person with a stable job and family life is likely to experience fewer structural changes and thus maintain a more consistent personality over time. Middle-aged workers are generally noted for keeping steady jobs, reducing natural rates of unemployment which contributes to life stability.