A:NO和O2
B:HCl和NH3
C:H2和CO
D:SO2和CO2
如图,Rt△MBC中,∠MCB=90°,点M在数轴﹣1处,点C在数轴1处,MA=MB,BC=1,则数轴上点A对应的数是( )
He was just falling asleep _____ there was a loud knock on the door.
如果△ABC∽△DEF,其相似比为3:1,且△ABC的周长为27,则△DEF的周长为( )