下列哪项肯定是原发性肝癌的促进因素（） A.大量饮酒 B.乙型肝炎病毒 C.

Walter offered us a lift when he was leaving the office, but ________our work, we declined the offer.[ ]

A．not finished  

B．not having finished

C．finished  

D．having finished

下列单位中属于国际单位制基本单位的是[ ]

A．牛顿

B．焦耳

C．库仑

D．安培

在Flash8中，影片的默认播放速度是15帧/秒

简述售后跟踪。