A:isn't
B:aren't
C:wasn't
D:weren't
动点P到两定点Aa,0,B-a,0连线的斜率的乘积为k(k∈R),则动点P在以下哪些曲线上( )(写出所有可能的序号)① 直线 ② 椭圆 ③ 双曲线 ④ 抛物线 ⑤ 圆
—Could you help me with my English?
—____________.
5和7相乘,积是多少? 5×7=35