A:氧化铝
B:氢氧化铝
C:铝
D:碳酸氢钠
一辆小汽车在平直公路上做匀速直线运动,10s行驶了90m,该汽车的速度是 ____ km/h,途径一座大桥,从桥头驶到桥尾共用6min,这座桥长 ____ km.
如图所示声波的波形图,下列说法正确的是( )
例:If I were in your position,I would pay close attention.
→Were I in your position,I would pay close attention.
下列说法中正确的是( )