题目

 The successful candidate will be adaptable, take ownership of and develop in the role by taking initiative, being motivated and ________ high standards.       A. ensured                    B. to ensure                  C. ensuring                   D. to be ensured 答案：C一辆摩托车行驶的最大速度为30m/s．现让该摩托车从静止出发，要在4分钟内追上它前方相距1千米、正以25m/s的速度在平直公路上行驶的汽车，则该摩托车行驶时，至少应具有多大的加速度？