疑问副词when、where、why、how用于构成疑问句。
当疑问副词构成的疑问句的谓语动词是be时，就在疑问副词后面加be动词：
How are you today?
Where are you from?
When is the wedding to be?
Why is your case so heavy?
当疑问副词构成的疑问句的谓语动词为一般动词时，疑问副词后面加助动词do、does、did，之后才是主语，主语后面放一个原形的一般动词，如：
Why does the tower lean?
When did you hear the news?
Where do you come from?
How did you come home yesterday?
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