分类：教育/科学-外语学习
问题：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
回答：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.