为什么~“SAYING IS EASY,DOING IS HARD”?真的很不理解啊!

为什么~“SAYING IS EASY,DOING IS HARD”?真的很不理解啊! 1.The island,joined to the mainland,is easy to go,为什么不能用joining?2.Sarah pretended to be cheerful,saying nothing about the argument.为什么不能用said?said不能看作是过去时吗？ Saying thanks is such an easy way to add to the world's happiness.中的Saying thanks为什么是ing形式这个我不懂. it's easy saying than doing,翻译 cartoons is easy to draw 为什么不对cartoons is easy to draw为什么不对? the question is easy to answer还是the question is easy to be answered为什么 this food is easy to digest,能否说this food to digest is easy.为什么 That knowledge is power is a famous saying.为什么句首要加that? it is easy said than done.为什么用done english is easy to learn,不定式为什么不用被动 the machine is simple to use.为什么不用easy. 我知道Learning a language is easy.这句是对的To learn a language is easy.和Language learning is easy.这两种说法对吗?为什么? doing is better than saying. 为什么This pen is easy to write with.可以变成This is an easy pen to write with? 为什么是It is easy to understand而不是It is easy to be understand为什么这里不用被动呢? Jim is _____ his mum about his friends.A.talking B.telling c.saying 为什么 What she is saying reminds me of my hometown.这里的remind为什么用复数? 英语翻译english is easy [ ] [ ] [ ] [ ] .