通过高考题精讲when引导的主语从句
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通过高考题精讲
when引导的主语从句
(2014全国大纲卷)24.
Exactly ______ the potato was introduced into Europe is uncertain, but it was probably around 1565.
A. whether
B. why
C. when
D. how
解析：本题选择C. 本题考查主语从句。
Exactly ______ the potato was introduced into Europe is uncertain
红色整个从句作主语系动词简化为：sth is uncertain
整个句子作is的主语，叫主语从句。
Exactly ______ the potato was introduced into Europe is uncertain, but it was probably around 1565.
A. whether
B. why
C. when
D. how
成分: 在从句中，作状语，有意思。
排除A.
句意：根据下文1565表时间。
Exactly when the potato was introduced into Europe is uncertain, but it was probably around 1565.
具体土豆什么时候被引进到欧洲不确定,但很可能是1565年左右.
小练习:
(2014陕西卷)15. ______ the delayed flight will take off depends much on the weather.
A. Why
B. When
C. That
D. What
解析：本题选择B. 本题考查主语从句。
______ the delayed flight will take off depends much on the weather
成分: 红色句子作depend的主语,是主语从句.在从句中作状语,排除CD.
句意:根据下文depends much on the weather，表时间。
When the delayed flight will take off depends much on the weather.
延误的航班将何时起飞很大程度上取决于天气状况。