三个相同的角组成了一个平角，这三个角一定是[ ]
A．锐角
B．直角
C．钝角
答案：A
The _______ look in her face suggested that she _______ it before. [ ]
A. surprising, wouldn't know
B. surprised, hadn't known
C. surprising, hadn't known
D. surprised, shouldn't know
《普通高中数学课程标准(实验)》设置了四个选修系列，其中选修系列1是为希望在人文社会科学等方面发展学生而设置的，下列内容不属于选修系列1的是______。
A．矩阵变换 B．推理证明C．导数及应用 D．常用逻辑用语
