黄帝的传说反映了黄河流域部落联盟的一段历史，其时间是  [ ]

A．约七千年前    

B．约五六千年前    

C．约四五千年前    

D．约四千年前

— Must I finish my homework before I go to play basketball ?

—Yes, you _____.  [ ]

 A.  needn't

B.  can't

C. must

D. may