A:twice as many a
B:twice as much a
C:twice as more a
D:twice much a
下列有关文学常识的表述,不正确的一项是( )
汽车从制动到停止下来共用了5s,这段时间内,汽车每1s前进的距离分别是9m,7m,5m,3m,1m.求汽车前3s和全程的平均速度.