A:33
B:31
C:29
D:27
当南极地区出现极夜现象时,下列说法正确的是( )
小鹭利用电流表和电阻箱测量小灯泡的功率,设计并连接了如图1所示的部分实验电路.
They are________ different sizes, shapes and metals, but they are exactly the same________.