Breakfast is ready, you’d better____.

A．not wake him up

B．not to wake him up

C．to wake him up

D．wake him up

电源给电容器充电使平行板电容器所带量为Q=4×l0^-6C，它的两极板之间电压U=2V，然后去掉电源。则它的电容为     μF；如果将两板电量各减少一半，则电容器所带量为      C，它的电容为     μF，两板间电势差变为      V；如果再将两板间距离增为原来的2倍，则它的电容为     μF，两板间电势差变为      V