Do you know _______ World Water Day is?-On March 22ndA.when B.where C.what D.which 为啥是when,他不是做时间状语嘛（不做句子成分的吧）?可是is后面缺一个表语啊,

Do you know _______ World Water Day is?-On March 22ndA.when B.where C.what D.which 为啥是when,他不是做时间状语嘛（不做句子成分的吧）?可是is后面缺一个表语啊,
Do you know _______ World Water Day is?-On March 22nd
A.when B.where C.what D.which 为啥是when,他不是做时间状语嘛（不做句子成分的吧）?可是is后面缺一个表语啊,

Do you know _______ World Water Day is?-On March 22ndA.when B.where C.what D.which 为啥是when,他不是做时间状语嘛（不做句子成分的吧）?可是is后面缺一个表语啊,
从答句可以看出,on the march 22nd,这是时间状语,所以就是when ,该句中,when = on which day

后面回答的是时间，疑问词就是when了
其实你可以这样看，when is World Water Day， do you know？把do you know 提到前面了，后面就变成陈述语序了，明白吗？