What's this It's pen .为什么答句不用this is pen,到底it,that ,this 的用法区别是什

What's this?It's a pen.(改为复数句) What's this?——___.(①It's a pen.②This is pen.③This is an pen.④It's a pen.) what's this in english a.It's pen b.It'sa pen c.I like pen 选哪个为什么? what 's this with English?It's a pen a.what 's b.with c.It's 挑错并改正 Its my pencil case.Whats in it?Look,this is a pen. what color is this pen的回答可不可以是It's a red pen what's this?It's a pen.为什么不能说是this is a pen.我们老师说就是不能说this is a pen.为什么 what's the p( )of this pen what is this ?It is a pen而不是It is pen.但为什么what's this? It's N.就是正确的?N前不能有冠词吗? what's_?__a pen ?a 、this;this is b 、this;it's c 、 that;that's d、 that' What's this It's pen .为什么答句不用this is pen,到底it,that ,this 的用法区别是什 What's this?It's letter P.what___is it?It's green.white.what's this letter?It's sletter N.It's red.P-E-N.is it''____''?Yes,it is.I have__blue pen .it's____to this is pen,it 's englishthis is pen,it 's english pen this is () pen,but it's ()broken pen this is( )my pen.it's( )pen.( )里填空 what's this in English?It's a pen.为什么不能说是this is a pen.?详细!this is 在哪能用?二者的区别是什么?谢谢啊! --It's a ball pen,( --It's a pencil.A.what is this B.and what is this C.what's it--It's a ball pen,( --It's a pencil.A.what is this B.and what is this C.what's it 英语改错-what's this?-t's yellow pen.