如图, 山坡AC与水平面AB成30°的角,沿山坡AC每往上爬100米,则竖直高度上升( )米
A:503
B:502
C:50
D:30
如图所示,变压器为理想变压器,交流电源的电压不变,L1、L2是完全相同的灯泡,V1、V2和A1、A2为理想电表,导线电阻不计.当开关S由闭合变为断开后,则( )
Jenny ______ with him at that time, for I was having dinner with her in my home.
下列关于能量转化的说法正确的是( )