After ____ series of unsuccessful attempts, he has finally passed ______ driving test.

A．/ ; the

B．a ; the

C．the ; a

D．/ ; a

如图所示，杨华在滑冰场上与同学进行快速滑行比赛，她和冰刀的总质量为45kg，已知每只冰刀与冰面的接触面积为15cm²。则她对冰面的压力大小为__________，她在单脚滑行时对冰面的压强是__________Pa。