从句做主语，求解HowandwhyJackcometochna_
How and why Jack come to chna ____ not konwn.When and where to build the new library ____ not been decid. 分别是填is/are，has/have? 为什么，请解释
分别是填is，has。都讲一个人或一件事，谓语用单数形式。一般，所述句子可改为：It is not known how and why Jack came to China.It has not been decided when and where to build the new library.