半通行地沟内,管道或保温层外表面至沟底的净距的取值范围为()。
A.50~100mm
B.100~150mm
C.100~200mm
D.200~300mm
参考答案:C
_____ his ability of speech, he has made use of each chance.
A.To improve
B.Improving
C.Being improved
D.Improved
一个物体从静止开始做匀加速直线运动,它在第1秒内与第2秒内位移大小之比为x1∶x2,在走完第1米时与走完第2米时的速度大小之比为v1∶v2,则下列说法正确的是:( )
A.x1∶x2=1∶3,v1∶v2=1∶2
B.x1∶x2=1∶3,v1∶v2=1∶
C.x1∶x2=1∶4,v1∶v2=1∶2
D.x1∶x2=1∶4,v1∶v2=1∶