单项选择题

(D)
THANK-you cards--heartfelt expressions of gratitude for gifts, services and general kindness--seem to be rare in an age when the Internet continues to reduce human interaction.
Although our society has changed greatly over the past century, the etiquette of thank-you notes has not.
While most people would agree that thank-you notes under these circumstances are a necessity, there are still those who forever postpone or are forgetful for unknown reasons.
And at no time of the year are thank-you notes more visible (or lacking) than June, the month of graduations, and the beginning of summer parties.
"It’s a must-do thing. A real thank you does not come by e-mail. It comes in the mail in an envelope. And what comes out of an envelope is a beautiful thing to touch and to handle and to pass around for everyone to read," said etiquette expert Letitia Baldrige.
Don’t think for a second that Baldrige is old-fashioned. Handwritten thank-you notes--any handwritten correspondence, for that matter- have taken on an air of extra importance and dignity (庄重) in this e-hyper (电子狂躁的) world.
Baldrige remains hopeful that the art may be enjoying a renaissance (复兴,再生).
More than simply obeying rules of etiquette, thank-you cards are a sign of caring.
"They’re more important now than ever," expert Peter Post says. "You are building a relationship. And part of building that relationship is that you acknowledge when someone has done something nice for you. "
"The payoff," Post says, "can be huge. The more we do it, the more it comes back to us, and it’s a benefit to us all. It makes our world a little bit nicer place to live in. " From the context, the word "etiquette" in the second paragraph probably means ______.