如图所示,电源电动势为E,内阻为r,当滑动变阻器的滑动端向右移动时,则( )
A:电压表V读数变大
B:电流表A1读数变大
C:电流表A2读数变大
D:灯泡L1消耗的电功率变大
如图所示为两类种子剖面结构图,据图回答:
He had hoped to have an opportunity to travel abroad for long. But it was a(n) ______ that he missed it when it came last month.
夏天,受潮的粮食和皮鞋常常发霉,这些霉菌是由什么发育而来的( )
在△ABC中,O为外心,P是平面内点,且满足OA→+OB→+OC→=CP→,则P是△ABC的( )