keep on 作主语时,为什么不用ing形式,而用原型啊?keep不是动词么 例句：Keep on walking until you get to the market这是祈使句么？

keep on 作主语时,为什么不用ing形式,而用原型啊?keep不是动词么 例句：Keep on walking until you get to the market这是祈使句么？ Compared with life on Earth,life on Mars will be better in many ways.为什么开头要用compared,而不用原型（祈使句）或ing形式（动名词作主语）? Get up early and you'll arrive there on time.不是动名词作主语吗?这里为什么不用? To keep in good health is very important.用it作主语改为同义句 eat more fruit and less meat to keep health 这个句子对吗?主语为什么不用eating dressed in a white uniform,he looks more like a cook than a doctor为什么不用dressing?这里不是动名词作主语? 英语翻译为什么用“in”不用“on”呢 in December 2011对吗?为什么不用on? keep fish in the lake养鱼为什么不用raise而是keep? All the students know_______(hand)in homework on time is necessary.答案说填handing,是动名词作主语,这里可以填to hand吗?为什么?不定式不是也可以作主语么? 英语动名词作主语问题Hold on to your dream and then you will sureiy achieve it.1、为什么这个句子里hold不用用动名词作主语?2、那在什么情况下要用动名词作主语?在什么情况下不用? 英语翻译不用‘我’作主语,怎么翻译 动词短语作主语用不用ing? The cat is in the tree?为什么不用on?这里为什么用in?不用on? keep healthy 为什么不用health? in the lesson为什么用in不用at或on? Keep going straight and you will see the police station on the right这句话 keep 不是动词吗,为什么放在第一个,为什么没有主语啊, i must keep on working hard ()it?at in on for为什么选at