2) keep doing指动作不间断地继续着。如：
It kept raining the whole night. 雨不停地下了一整夜。
3)keep on doing 与 keep doing 二者可以换用；一般都不接表示静止状态的词，如
standing; sitting, lying, sleeping等。如：
Why do they keep (on) laughing all the time? 他们为什么老是笑个不停?
Ive learned about 1,000 words, but I keep (on) forgetting some of them. 我大约学了1000个单词，可有些单词老是记不住。
advice，advise
均可表示“建议、劝告”之意 ，其区别是：
l)advice为不可数名词，无复数形式，不能与定冠词连用。请记住下列结构：
a piece of advice 一条建议 two pieces of advice 两条建议
some advice 一些建议 follow/take ones advice 听从某人劝告
give sb. some advice on sth./give sb. advice on doing sth./ give sb. advice on how to do sth. 就… …给某人提建议
2)advise是动词，常用于下列结构中：
advise +名词/代词
advise sb. to do sth. &nb
，Unit 21 Karl Marx－教学教案