Mrs. Smith has _________ all the shampoo, so she’ll have to buy some more.

A．run out

B．used up

C．given out

D．sped up

如图所示，用力F把物体紧压在竖直的墙上不动，那么，当F增大时，铁块对墙的压力F_N及物体受墙的摩擦力f的变化情况是

A．F_N增大，f不变

B．F_N增大，f增大

C．F_N减小，f不变

D．以上说法都不对