It's polite to send thank you notes
Zachary just had his birthday and received a generous check from his grandparents.
Zachary wants to express his gratitude to his grandparents for his birthday present.
Zachary takes some time in the evening to write his grandparents a note thanking them for their present.
Zachary waits until the next time he sees his grandparents and thanks them for their gift.
Zachary's grandparents are touched by his polite gesture and are proud of how well mannered he's become.
Zachary's grandparents tell his parents that they should probably be teaching him to be more polite and timely with his gratitude.