A:−35
B:35
C:−45
D:45
—Who's that girl? — She's my____(sister/ brother).She's a student.
It is ______ elephant.( )
如图所示的电路中,当灯泡L1烧坏时(设电源电压U不变),则通过 L2的电流( )
下列说法正确的是( )