The （） in e-mail messages has affected almost every computer around the world and has caused the damage of up to US$1 billion in North America.

A．illness

B．virus

C．weakness

D．attachment

汉语中的词类（词的语法分类）可以首先分出的两个大类是（）

A．基本词和非基本词

B．实词和虚词

C．典型词和兼类词

D．体词和谓词