题目

如图所示，一块小磁铁吸附在竖直放置的磁性黑板表面，且沿着磁性黑板表面匀速下滑，磁铁与磁性黑板间存在着A．一对相互作用力B．二对相互作用力C．三对相互作用力D．四对相互作用力  答案：C解析:略 —The constant noise around here______ me crazy!—Calm down.It’s no use complaining.A.drove B.drives C.is driving D.had driven