题目

 If it __________for the snow, we ___________the mountain yesterday. A. were not; could have climbed    B. were not; could climb C. had not been; could have climbed    D. had not been; could climb 答案：C 如图，在半径为R的半圆形碗的光滑表面上，一质量为m的小球以角速度ω在水平面内作匀速圆周运动，则球所在平面离碗底的距离h=______