請看下面一道題：I don’t know if he _________ tomorrow.
A. come??????????????? B. comes?????????????? C. will come???????????? D. is coming
【分析】此題容易誤選B。認為 if 引導(dǎo)的是條件狀語從句，從句謂語要用一般現(xiàn)在時表示將來意義。其實，此題應(yīng)選C，句中if引導(dǎo)的不是條件狀語從句(即if≠如果)，而是賓語從句(即if＝是否)，句意為“我不知道明天他是否會來。，句意為”請看以下類似試題：

(1) I don't know if she _________, but if she _________ I will let you know.
A. comes, comes?????????????????????????????? B. will come, will come
C. comes, will come????????????????????? D. will come, comes
答案選 D，第一個 if 引導(dǎo)的是賓語從句，第二個 if 引導(dǎo)的是條件狀語從句。

(2) “When _________ he come?” “I don’t know, but when he _________, I’ll tell you.”
A. does, comes???????????????????????????????? B. will, will come
C. does, will come???????????????????????????? D. will, comes
答案選 D，第一個 when 疑問副詞，用于引出一個特殊疑問句；第二個 when when 是從屬連詞，用于引導(dǎo)時間狀語從句。

(3) “When he _________ is not known yet.” “But when he _________, he will be warmly welcomed.”A. comes, comes????????????????????????????? B. will come, will come
C. comes, will come???????????????????????? D. will come, comes
答案選 D，第一個 when 引導(dǎo)的是主語從句，第二個 when引導(dǎo)的是時間狀語從句。

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