题干
When you break the rules, you should ___ to your teacher.
A：apologise
B：introduce
C：expect
D：compare
答案(点此获取答案解析）
A
When you break the rules, you should ___ to your teacher.
A：apologise
B：introduce
C：expect
D：compare
平面
，
与两平面
所成的角分别为
和
，过
分别作两平面交线的垂线，垂足为
，若
，则
