题干
The reason why she had a headache was _______ she had been read
ing for too long.
ing for too long.
A：that
B：which
C：because
D：for
答案(点此获取答案解析）
A
（其中
）所表示的圆锥曲线（椭圆、双曲线、抛物线）方程中任取一个，则此方程是焦点在
轴上的双曲线方程的概率为