— The boy can speak both English and Japanese he is only ten.
— Wow, what a clever boy!
A:if
B:because
C:although
D:so
45−x=27
x= ____
如图所示电路中,电源电压恒定,R1为定值电阻,R2为滑动变阻器.闭合开关S后,滑动变阻器滑片P自b向a移动的过程中( )