As is known to all,the whale is not fish but a mammal.
问题描述：
As is known to all,the whale is not fish but a mammal.
这句话中为什么fish前面不加a而mammal前面要加a呢?
答
fish指它不是鱼类,这是种类没有特指.
后面的A是指WHALE,whale是一种哺乳动物.