[单选题]
A ball is thrown downward from theknjnl 1y:pcb:h* .q7 t*xuzhts5s/xb,vj *f 9top of a building with an initial speed of 25 m/s. It strikes the ground after 2.0 s. How 9xs* uv,/f tjxhz5b*s high is the building?
A. $20 \; m$
B. $30 \; m$
C. $50 \; m$
D. $70 \; m$
