He remembered past kindness of a friend. And wrote him a thankyou letter.

他记起一位朋友昔日的恩情，便写给他一封信表示感谢。

youdao

Be appreciative and say "thankyou" for any gift you receive. In the age of email a handwritten thank-you note can have a powerful effect.

收到任何礼物，都要感嗯，并说“谢谢”。在有电子邮件的年代，手写的“感谢卡”价值尤显贵重。

youdao

Be appreciative and say "thankyou" for any gift you receive. In the age of email, a handwritten thank-you note can have a powerful effect.

收到任何礼物，都要感恩，并说“谢谢”。在有电子邮件的年代，手写的“感谢卡”价值尤显珍贵。

youdao

And Citi's ThankYou Premier and Chase Sapphire Preferred cards provide more buying power when points are spent on travel.

WSJ: The New Credit-Card Rewards Programs