It is universally believed that a student with an extremely ________ mind usually gets high scores in the exams, especially in the physics exam.

A．sharp

B．shallow

C．narrow

D．awful

写出下列变化的化学反应方程式。

（1 ）用砂纸打磨过的铝片放置在空气中:________________________________________ 。

（2 ）铁钉在稀硫酸溶液中：___________________________________________________ 。

（3 ）铁丝浸泡在硫酸铜溶液中：_______________________________________________。