北京托大现代远程教育 l.Cultural background(文化背景) Warm-up questions: Have you ever received an invitation card? How did you reply to the invitation? How to write an invitation card?如何写邀请函？ I. Cultural background （文化背景） Warm-up questions: Have you ever received an invitation card? How did you reply to the invitation? How to write an invitation card?如何写邀请函？