【正确答案】Dear Mr. Biggs,
   I am very glad to receive your invitation to take part in the annual business management seminar.
   I am going to give a talk on the intercultural business management in the globalization. And I would like to know how long the talk should be, so that I can make good preparations for it. Concerning accommodation, I would be very grateful if you have some arrangements. Thank you for your invitation. I look forward to seeing you again.
   
   

【答案解析】商务信函写作的时候需要注意以下几个原则，即7C原则：
   1．Courtesy礼貌：语气适当，态度真诚。
   2．Consideration体谅：多考虑收信人的要求，同时要强调积极的方面。
   3．Completeness完整：包含所有需要表达的信息。
   4．Clarity清楚：避免使用含有歧义的字句。
   5．Conciseness简洁：避免使用冗长句子，避免不必要的重复。
   6．Concreteness具体：信函传达的信息要具体、鲜明。
   7．Correctness正确：避免拼写、语法和标点符号等错误。