However ____  important school life may be, ___ great influence of parents can’t be ignored or discounted by the teacher.

A．an; a

B．the; the

C．an; /

D．/; the

火山活动还可以形成多种矿产，海底火山喷发的玄武岩，常可形成规模巨大的铁矿和铜矿。