What Does the "Rule of Three" Recommend

What does the "rule of three" recommend?

A) It recommends that you should drink 3 cups of milk daily.
B) It recommends that older adults should exercise 3 days each week to prevent weight gain.
C) It recommends that if you want to change a behavior, you might need to try the new behavior 3 times before you can accept it.
D) It recommends that individuals on weight-loss diets should eat at least 3 meals daily to maintain their energy levels.