英语中冠词的区分
1、Knowledge is power.(在泛指的抽象名词前,不用冠词)
但有时候：Many people agree that a knowledge of English is a most in / international trade today.
2、A plane is a machine that can fly.（概括食物的整体,表一类）
3、The horse is an useful animal.（此时表示一类人或事物）