What is this /that in english?答句可用什么主语

This is what I This is what I what This is exactly what I need.为什么不说 This is that I need.这是什么句式 I don't know,what's the situation.What is this?Why is that I have no idea_______.A.what does this word meanB.what this word meansC.what kind of a meaning is this wordD that is this word means This is just what I This is what I am This is what I think. that is what i am What is this/that?与What is this/that in English?What is this/that?与What is this/that in English? 这两句求解, This plus that is twenty-one,this minus that is five.What is this and what is that? what is this 回答 与what is that 回答 This is what I should do.Is what I This is the only thing ()I have nowA./ B.what C.which D.that which Listen!This is ___ I want to sayA.that B.who C.which D.what what i want to say is ___,you must study hard.this or that? This is all ( )I know about the accident.填that或what请说明为什么 This is something ( ) I must decide caught 填that,which,what,when 为什么