It is really disturbing to me that my once best friend _______ to me recently. Worse still, I don't know

what I have done wrong.    [ ]

A. avoids to talk      

B. escapes talking       

C. stops to talk      

D. avoids talking

在寡头垄断市场上，生产相似产品的企业为了控制市场，获取最大利润，联合起来结成同盟提价限产的方式称为( )。

A．卡特尔

B．价格歧视

C．纵向一体化

D．掠夺性定价