"As we express our gratitude, we must never forget that the highest appreciation is not to utter words, but to live by them." Which of the following is the correct interpretation of the quote above?
a. Saying thank you to someone is the highest form of flattery you can give to them.
b. When you are thankful to someone, you shouldn't tell the person.
c. As we live our lives, we should expect people to be grateful to us.
d. The greatest way to show your gratitude to someone is to live out the qualities you have recognized in that person as valuable.