Our family makes it a________to turn off the television at mealtime and try to speak as little

as possible.[ ]

A．privilege  

B．pressure

C．procedure  

D．principle

目前造血干细胞移植常规使用的HLA分型方法是（）。

A.微量淋巴细胞毒试验

B.流式细胞术

C.细胞分型法

D.血小板免疫荧光试验

E.基因分型法