Question

16．Where's my pencil box？I ______ know．（　　）

• A． aren't
• B． don't
• C． isn't
• D． be not

Answer 1

分析 ---我的鉛筆盒在哪里？
---我不知道，

解答 答案：B，表達的是客觀事實用一般現在時，know是實意動詞，主語I，借助于do構成否定，故答案是B．

點評 1． 簡單句中含有系動詞be、情態動詞和助動詞時，變否定句時需在系動詞be、情態動詞和助動詞后加not．如：I am a teacher．→I am not a teacher．
He can help me．→?He can't help me．

2．簡單句中謂語動詞為行為動詞時，要根據時態選用do的相應形式，把肯定句變為否定句．如：
The little girl wants to go there．?→The little girl doesn't want to go there．
He did his work yesterday．→?He didn't do his work yesterday．

3．祈使句變否定句時，一般在句首加Don't，但Let us或Let's開頭的祈使句在 Let us或 Let's后加not即可．如：
Put them over there．→?Don't put them over there．
Let us go home．→?Let us not go home．