There is a saying that      "Never put off until tomorrow what you can do today."

A．will go

B．has gone

C．is going

D．goes

请在如图中，小明的身体可作为一个杠杆，O点是支点．他的质量为50Kg，所受重力可视为集中在A点．将身体撑起时，地面对双手的支持力至少多大？