题目

 It was not his looks but his voice __________ attracted me.   A. that                        B. who                       C. as                         D. which 答案：A在圆的摆线上有点(π,0),那么在满足条件的摆线的参数方程中,使圆的半径最大的摆线上,参数φ=对应点的坐标为_________.