为什么可以说What's this?而不可以说What's it?

为什么可以说What's this?而不可以说What's it? 为什么不可以说what name are sit on the floor为什么不可以说sit on floor?the在这里做什么用?还有,为什么不可以说What`s problem? Phone #对不?为什么不用at?what's this in English?怎么回答?有this is的形式么?还有who's this?是不是用it's的回答而不用this is? 为什么动物可以说一条,人不可以说一条,而生命可以说一条 What's this?It's a box.为什么回答中要用It's,而不用this is a box 英语翻译为什么答案选what color is it 不选 what's this 与What’s this in English?It’s pen.有关的几个问题这个答语对否?pen前必须加冠词吗?为什么必须用It’s而不能用this is来回答? what is this?可以写成 what's this?为什么? this is Sam's ___visit to Beijing.he hai been there twice before为什么是third为什么不可以说third time?不可以说是第三次么？ What's your job可以说成 What job are 如果不行的话,那为什么What nationality are you?可以说成What's your nationality呢? 这个用英语怎么说What `s this in English这个用英语怎么说?What `s this in English?用How to say it in English?为什么不可以 what events为什么有s而what year没s 打招呼可以说：what's new about you What letter is it?What's this letter?It's VIt's a VIt's an VWhat's this letter?It's UIt's a UIt's an UWhat's this letter?It's HIt's a HIt's an H为什么不能用It's V(U,H) This picture looks beautiful和The clothes feel soft.为什么look后面加s而feel后面不加s. 为什么不可以说a doctor asked what the matter was with you what's this?