Final answer:
By the time a person turns 60, most get between five to seven hours of sleep a night, which corresponds to answer option (d).
Step-by-step explanation:
The amount of sleep an individual gets can change significantly as they age. Research shows that as people reach the age of 60, their average nightly sleep duration declines to less than 7 hours. Given the options presented in the question and referring to the provided reference material, the best answer would be (d) five to seven hours. It's important to note that while sleep needs diminish with age, the National Sleep Foundation indicates that most adults still require between 7 and 9 hours of sleep per night. However, this is an average, and actual sleep needs can vary from person to person.