You have won the first prize in the game you didn’t mention in your speech yesterday.A.

问题补充：

You have won the first prize in the game, you didn’t mention in your speech yesterday.

A. as

B. since

C. what

D. which

答案：

A. as

B. since

C. what

(答案→)D. which

解析：考查定语从句。本题是一个非限制性定语从句，as有正如的意思，与句意不符。BC不是定语从句的关系词。which指代前面一句话的内容作为mention的宾语。句意：你在比赛中赢得了第一名，在你昨天的研究中你没有提及这一点。故D正确。