All the pictures in this book, ______ otherwise stated, come from those taken by Miss Brown.

A．unless

B．until

C．even if

D．as if

两盏白炽灯甲和乙，分别标有“220V  10W”和“220V  100W”串联接在220V的电源上，两灯的实际功率之比P_甲：P_乙为______．