—Why does Kate look upset?

—Perhaps she has made ______ mistakes in her graduation exams. [ ]

A. little

B. a little

C. few

D. a few

下列关于内存和外存的叙述，错误的是________。

A．断电后存放在外存中的信息不会丢失，可以长期保存

B．外存的容量比内存大的多，甚至可以说是海量的

C．外存速度慢，内存速度快

D．内存和外存都是由半导体器件构成的。