单选题You have to explain 

问题补充：

单选题Youhavetoexplain____usthereason_____yourbeingabsentfromschoolyesterday.A.to; ofB.to; whyC.for; thatD.to; for

答案：

D解析explain sth to sb 把......向某人解释，所以第一空用to；the reason _____ your being absent from school yesterday.你昨天上学迟到的原因，……的原因，用for the reason。所以选D。