This college allows students to develop their own interests, to ______　extent they wished．

A．whoever

B．whatever

C．however

D．whenever

常温下，将等质量的铜片、银片、铁片、铝片分别置于四个小烧杯中，然后分别加足量的浓硝酸，放出

NO₂气体最多的是 [ ]

A．铜片 　　　　

B．银片 　　　　

C．铁片　　　　

D．铝片