The children are celebrating the National Day(划线).(对划线部分提问)

问题描述:

The children are celebrating the National Day(划线).(对划线部分提问)
——— ————————the children ————————
celebrating the National DAY 划线

若是对children 提问,Who are celebrating the National Day?
若是填空,What is the children celebrating?celebrating the National DAY 划线what are the children doing?