题干
—Must we leave the classroom now?
— No, you _____. You _____ leave after the bell rings.
A：mustn't; are allowed to
B：don't have to; might
C：needn't; can
D：can't; are supposed to
答案(点此获取答案解析）
C
轴的非负半轴为角的始边，如果角
、
的终边分别与单位圆交于点
和
，那么
等于