高中英语 It is well known that a good ( )of English is a must in international trade nowadays.

问题描述:

高中英语 It is well known that a good ( )of English is a must in international trade nowadays.
knowledge是不可数名词,为什么前面可以用a

不可数名词使用冠词表示一类事物,而且有些不可数名词前加形容词,前面就可以用冠词,比如三餐前不加冠词,但是如果有形容词就可以加冠词