下列处理不会造成环境污染的是( )
A.化工厂排放污水
B.新型燃气车用氢气为燃料
C.喷洒农药
D.燃放鞭炮
答案:B
图1.5-12所示电路中,t=0时闭合开关S,u1(0-)=u2(0-)=0V,则u1(0+)应为()V。
A.6
B.4
C.0
D.8
Don't play football near the river. Why not _______ it on the playground?[ ]
A. plays
B. playing
C. to play
D. play