题目

What difficulty I had _____ the dirty walls! I had no choice but to have it ____ again.         A. clean, paint                                  B. cleaning, painting               C. cleaned, to paint                             D. cleaning, painted     答案：D如图，质点P在半径为2的圆周上逆时针运动，其初始位置为P（，-），角速度为1，那么点P到x轴距离d关于时间t的函数图象大致为（ ）A．B．C．D．