knowledge是可數還是不可數

　　There is a lack of knowledge about the tax system.

　　大家對稅制缺乏了解。

　　For years we had little knowledge of what life was like inside China.

　　以往很多年我們對于中國國內的生活情況所知甚少。

　　He never made a will, to the best of my knowledge.

　　據我所知，他從未立過遺囑。

　　She has acquired a good knowledge of English.

　　她英語已經學得很好。

　　Our knowledge of the disease has advanced considerably over recent years.

　　近年來我們對這種疾病的了解深入多了。