We usually play sports_____two hours after class.[ ]
A. for
B. in
C. of
D. at
答案:A
某车床上的灯泡有“6V 6W”的字样,如果把这个灯泡接到电压为12V的电路上并使其正常发光,需要串联的电阻的阻值为( )
A.10Ω
B.12Ω
C.0.6Ω
D.6Ω