[单选题]Which of the following is NOT a business letter?Xyx答案窝(daanwo.com)-大学生作业答案及考资分享平台 AA letter of inquiryXyx答案窝(daanwo.com)-大学生作业答案及考资分享平台 BA letter of recommendationXyx答案窝(daanwo.com)-大学生作业答案及考资分享平台 CA letter of applicationXyx答案窝(daanwo.com)-大学生作业答案及考资分享平台 DA letter to your boyfriend or girlfriend