题干
— _______does your brother watch TV every evening?
— Less than an hour.
A：How much
B：How long
C：How many
D：How often
答案(点此获取答案解析）
B
有两个不等实根，则k的取值范围是（ ）
，当直线l与圆
有两个交点时，其斜率k的取值范围是