an good idea正确吗

an good idea正确吗 是an good idea还是a good idea? 是an good idea 还是 a good idea ,为什么 What about going to the zoo?--Good idea 为什么不说That's an good idea? good idea good idea 这里的an是修饰哪个词?an good idea和an beatiful island请问这里是不是修饰idea和island?所以用an.如果是修饰idea和island，good和beatiful不是元音开头，还是要用a吗？ good idea or great idea 这句话用a/an?It is a good idea for the graduates to learn more knowledge with a higher degree .这里不是修饰idea吗,为什么不是an? That's a good idea.为什么不用an,难道这里的不定代词是用来修饰good?什么时候可以用 an+形容词+idea have a knowledge of 和 have an idea of用在“了解”这个意思,knowledge和idea用法有什么区别吗?比如：have a knowledge of / have a good knowledge ofhave an idea of / have no idea of另外,有have no knowledge of这种用法吗? a good idea a good idea good idea翻译英文 Good idea意义用法 good idea怎么翻译? a good idea 翻译 that good idea