A:Having told many time
B:Having been told many time
C:He had been told many time
D:Many times as he was told
When you can't hear clearly. What should you say? __________
读印度季风图完成下列各题。
如图,已知矩形纸片的一条边经过直角三角形纸片的直角顶点,若矩形纸片的一组对边与直角三角形纸片的两条直角边相交成∠1、∠2,则∠2﹣∠1=____ .