a few/ few/ a little/ little
Ⅰ. a few和few修饰可数名词，a little和little修饰不可数名词；a few和a little表示肯定意义，few和little表示否定意义，可受only修饰。如：
① Few people will agree to the plan because its too dangerous.
②This text is easy to understand though there are a few new words in it.
③ There is little water left in glass. Will you please give me some
④ Dont worry, we have a little time left.
about/ on
Ⅰt 关于表示的内容较为普通或指人时用它。侧重于叙事，多用于叙述个人经历和事迹，故事内容涉及一些较浅的问题。是非正式用语。
You use about to introduce who or what something relates to or concerns.
She knew a lot about food.
He never complains about his wife.
Ⅱ 关于侧重于论述政治理论，国际形势，学术报告等。也就是说，当表示这本书，这篇文章或演说是严肃的'或学术性的可供专门研究这一问题的人阅读时用。eg:
This is a text book on African history. 这是一本关于非州历史的教科书。[注]：它们有时可通用。
He declined to give any information on the Presidential election.
