第一句中 正常語序為：That is what book on the table.可以看出,that是指示代詞做主語,不能改.
第二句中 which the teacher explained yesterday 可以看作表語從句.Is this problem （ ）the teacher explained yesterday?A thatB the oneC which那為什么不選which正確的答案應(yīng)是B， the one。這樣，the one就作了表語，后面的the teacher explained yesterday作定語從句，修飾the one，關(guān)系代詞作explain的賓語省略了。在這里不能用which. which一般是對定語提問。如：The book on the desk is mine. 如果對句子on the desk提問的話，要用which, 即：Which book is yours？而在（ ）the teacher explained 句中， 括號內(nèi)是做explained的賓語，所以不能用which, 但可以用what. 我是語法通霸一書的編者，如有疑問，可以繼續(xù)問我。