Question

8．The river used to be so clean．（改为否定句）
The riverdidn't/useduse/notto be so clean．

Answer 1

分析 这条河过去很干净
这条河过去不干净．

解答 答案：didn't use/used not．原句中used to do sth．句型表示"过去常常，过去习惯做某事．"它的否定式：used not to do sth或者didn't use to do sth．故答案是didn't use/used not．

点评 本题考查的是句型used to do sth的否定式．它的否定式：used not to do sth或者didn't use to do sth．