What's this?It's a box.为什么回答中要用It's,而不用this is a box

选择题What's this?A.It's Z.B.It's red.C.This is ruler. 选择 What's this - ( )A A.It's B.It's an C.It's a D.This is -What's this?-It's a-------. What's this( )a photo?A.It's B.it's C.Its A:What's this?B:Oh.( )It'sA:What's this?B:Oh. ( )It's my pencil. what 's this with English?It's a pen a.what 's b.with c.It's 挑错并改正 It's coffee.__?It's milk.A.Who is this B.What's it.C.And what's mine D.And what's this 选哪个 It's a football.______?——It's a basketball.A.What's this B.And what's that C.This is what A:What's this in English B:It's a jacket.A:What color is it B:It's blue A:Yes,it's a___ what's this?A.It's here B.It's the letter S C .its S D.It's a S 应该选哪一个 what's this?A this is key B it's key应该选几 1.what's that a.this is1.what's thata.this is b.it is c.lts d.lt's 选择题What's this?A.It's Z.B.It's red.C.This is ruler.速度、、、、、、、、、、、、! What's this in English?________ A.It's black B.It's a map C.It's 810-2796 D.It's blue What's this in English?It's a(n)A:map B:CD C:ID card What's this?It's______S.A.a B.an C./ D.the What's this?It's ( ) UFO.A.a B.an C.the What's this?It's( ) UFO.A.a B.an C.the D./无