The answer to your question is: A) Your food journal.
It's best to use a food journal to keep track of the things you've eaten, and how much calories you've eaten throughout that day. Using a journal can help you when your on a diet so you can keep track of what you've been eating.
I hope this helps you!
Have a wonderful day!
-LizzyIsTheQueen
Given the attitude of the grandfather portrayed in the problem, the most likely answer is
B) Go to the doctor regularly because he can monitor his health before problems get severe.
This would be because you are reminded, "prevention is the best medicine", and the answer B provides the precaution that is recommended.
The independent variable is the exercise program (high vs low)
The dependent variable is what they are measuring so it would be the subjects stamina. The dependent variable is measured by how long they can walk comfortably on a treadmill (at the end of the program).