Final answer:
Constipation is a disorder associated with aging due to the digestive system slowing down, muscle inefficiency in the digestive tract, and changes in cellular structure as well as overall functionality.
Step-by-step explanation:
The disorder associated with aging from the options provided is constipation (A). As individuals age, the digestive system slows down, and the muscles in the digestive tract do not work as efficiently, often leading to constipation. Other conditions, like Parkinson's disease and Grave's disease, are also associated with aging, but they are not listed among the options given.
Furthermore, susceptibility to diseases and the common causes of death vary at different stages of adulthood. Factors such as cellular changes, decreased functionality, and a compromised immune system play a significant role in the aging process. The "graying of the United States" refers to the growing percentage of the population over sixty-five, highlighting the importance of understanding the health issues associated with aging, including constipation.