Exercise is a doorway to good health这句话怎么翻译,里面的doorway怎么解释?

初三英语转换句子题Exercise A is easier than Exercise B-> Exercise A is _____ _____ than Exercise B The twins uncle every day A.exercise B.exercises C.is exercise D.is exercisesA.exercise B.exercises C.is exercise D.is exercises this is good exercise 为什么不是this is a good exercise ? SWIMMING IS _____ A a good exercise B good exercise Cgood exercises D a good exercises What you need is more_____.You are always doing your______at your desk.A.exercise;exercise B.exercises;exercisesC.exercises;exercise D.exercise;exercises为什么选D? If you want to be healthy,（）is（）.A.do more exercise；helpingB.do more exercise；helpfulC.doing more exercise；helpfulD.doing more exercise；helping This is _____easy exercise填an还是a Riding a bike is exercise.为什么Riding不能用ride? walking is good exercise.为什么不加a? Li Ming often does exercise,so he is very a ( ) Walking is good exercise.为什么不用加冠词a啊? 连词成句 Going ,is ,for ,walk,a ,exercise 连词成句 Going ,is ,for ,walk,a ,exercise It is good_____(exercise) Is it a universal ___(true) that exercise is good for you?PS:原因 ________（Taking a walk,Take a walk) is a good exercise for people of all ages. 1.The exercise is a piece a cake.2.The exercise is very easy这两个句子的意思一样吗? 以Exercise is a good way to keep healthy为题目以Exercise is a good way to keep healthy为题目,写一篇60词短文