一物体以初速度20m/s竖直上抛,当速度大小变为10m/s时所经历的时间可以是( )
A:1s
B:2s
C:3s
D:4s
下列自然景观中属于北方地区的是( )
—It must be the repairman. I ______ him to come to fix our fridge two hours ago.