单选题 The reason why even the best auctioneer cannot stop the "knock-out" is that _________.

A、 he has been deeply involved in it
B、 the dealers do not know the true value of the article
C、 he is not familiar with the regular buyers of the goods
D、 the dealers make the arrangement behind his back

【正确答案】 D

【答案解析】[解析] 文章第四段第六行“whereby dealers illegally arranged beforehand not to bid against each other，．．．”说明，各竞买人暗地里商议好现场不互相竞价，而指定其中一名买家以低价买到拍卖品，最后在他们内部再进行竞买。