某人估测一竖直枯井的深度,从井口静止释放一石头并开始计时,经过2s听到石头落到井底的声音,由此可知井深约为()
A.10m
B.20m
C.30m
D.40m
参考答案:B
农业发展受制于资源分配不均衡。
How come you stepped into the lab with your shoes on ? You’re to take them off before you enter it . I told you so !
A.expected
B.supposed
C.forbidden
D.permitted