Janet Is 73 Years Old

Janet is 73 years old. Her son has observed a relatively sudden change in her tempo of movement recently. She has begun to move more slowly and change position very deliberately. What is the most likely explanation for her behavior?

A) She is purposefully attempting to prevent dizziness due to normal respiratory and circulatory degeneration.
B) She is too tired to move any faster.
C) She is thinking, "At my age, why should I rush?"
D) She is showing signs of senility due to neural degeneration.