【单选题】

Many years ago, when I was fresh out of school and working inDenver, I was driving to my parents’ home in Missouri forChristmas. I stopped at a gas station (加油站) about 50 miles from OklahomaCity, where I was planning to stop and visit a frienD、While I was standing in line at the cash register (收款台) I said hello to an older couple who were also paying for gas.

I took off, but had gone only a few miles when black smoke poured from the back of my car. I stopped and wondered what I should do.A、car pulled up behind me. It was the couple I had spoken to at the gas station. They said they would take me to my friend’s. We chatted on the way into the city, and when I got out of the car, the husband gave me his business carD、
I wrote him and his wife a thank-you note for helping me. Soon afterward, I received aChristmas present from them. Their note that came with it said that helping me had made their holidays meaningful.
Years later, I drove to a meeting in a nearby town in the morning. In late afternoon I returned to my car and found that I’d left the lights on all day, and the battery (电池) was deaD、Then I noticed that the Friendly Ford dealership—a shop selling cars—was right next door. I walked over and found two salesmen in the showroom.
"Just how friendly is Friendly Ford " I asked and explained my trouble. They quickly drove a pickup truck to my car and started it. They would accept no payment, so when I got home, I wrote them a note to say thanks. I received a letter back from one of the salesmen. No one had ever taken the time to write to him and say thank you, and it meant a lot, he saiD、
"Thank you" —two powerful words. They’re easy to say and mean so much.
By telling his own experiences, the author tries to show ______.A．how to write a thank-you letter
B．how to deal with ear problems
C．the kind-heartedness of older people
D．the importance of expressing thanks