题目

There is a new problem involved in the popularity of private cars ______road conditions need______. A. that; to be improved                                         B. which; to be improved C. where; improving                                                D. when; improving 答案：A将棱长为2的正方体木块削成一个体积最大的球，则这个球的表面积为（　　）A．2πB．4πC．8πD．16π