不定项选择 前脚膝尖超过脚尖和膝尖与脚尖不在同一方向上是两种最常见的不正确弓步动作。

单项选择题 单相桥式整流电路变压器次级电压为10V(有效值),则每个整流二极管所承受的最大反向电压为( )。A. 10VB. , 14.14VC. 20VD. 28.28V

单项选择题 According to the passage， which of the following factors might spoil the tourist’s fun at Mediterranean resorts and beaches ？ A. Polluted water B. Crowded buses C. Traffic jams D. Rainy weather