[单选题]Look at the following parts of a letter. Arrange them in a logical order.dp5答案窝(daanwo.com)-大学生作业答案及考资分享平台 a. Reason for writingdp5答案窝(daanwo.com)-大学生作业答案及考资分享平台 b. Requests or actionsdp5答案窝(daanwo.com)-大学生作业答案及考资分享平台 c. Concludingdp5答案窝(daanwo.com)-大学生作业答案及考资分享平台 d. Opening greetingdp5答案窝(daanwo.com)-大学生作业答案及考资分享平台 e. Closing greeting