人体各个部分之所以如此协调,主要是神经系统调节和____调节的结果.
My students,________you have a heart loving life,you always can find things that would make you happy each day.
在如图所示的电路中,电源电压恒定,L1、L2均标有“6V 6W”字样(设灯丝的电阻不变)。当S1、S2闭合时,灯L1正常发光;则S1闭合,S2断开时,两盏等的总功率是( )