为什么要用It's a Y

为什么要用It's a Y It's a lovely baby的it是什么意思,为什么要这样用? It's a new bike.Do you want a go?为什么要用a go? It's fine weather for （a) walk?为什么用A? It's a circle.可以说成It's circle.为什么? it's a () time to go to bed为什么要用 fun 或funny It's+been++a+long+time.been在这里起什么作用?为什么要用been It's a room with things lost and found.为什么要用with it's a pity 为什么pity要加a,it's a help和it's a pity是一样的形式吗?为什么有的名词可以直接It's n.不用带数. It's a must to have a good knowledge of English nowadays.(must前面为什么要用a) 一个英文句子解释it's really been a while,try again.这里为什么要用been.为什么不用it only take a while. -who's that over there?-It's Lucy's sister.这里回答为什么要用It's She's可不可以用呢?为什么? It's () hot.为什么要用really 而不用real --what's this?--_____is a pen.为什么要填these?为什么不能填it? _____ that she has received a doctor's degree.答案是选B,为什么要去掉aA.It’s a splendid news B.It’s splendid news it`s such beautiful a night it`s so beautiful a night 为什么这句对 It's so cheap a book.和It's so a cheap book.哪个对?为什么? 求大神指教.It's. a picture of a classroom为什么用of