下列必须加入氧化剂才能实现的是 ( )
A.Fe3+Fe2+-
B.SO2SO42-
C.H2O2O2
D.SO2SO32-
答案:B
The poet and_________pianist is going to give us a talk this afternoon.
A.a
B.the
C.不填
D.an
阻值为10Ω的一只小灯泡,正常发光时两端电压为5V,现将该小灯泡接在15V的电源上,为了使小灯泡正常发光,应______联一个阻值为______Ω的电阻.