A:in what
B:in which
C:what
D:where
方程x2+y2+2ax﹣4y+(a2+a)=0表示一个圆,则a的取值范围是( )
下列数据中与实际情况最接近的是( )
— Do you think it is going to rain tomorrow?— ___________. We are going camping tomorrow.
判断:随着k1、k2取值的变化,四边形ADBC能否为正方形?若能,求点A的坐标;若不能,请简要说明理由.