is surprising to us is that Tom, for English was once boring, can speak English fluently as though he were a native speaker.
A. What; whose
B. What; whom
C. It; whose
D. As; whom
网友回答
A. What; whose
(答案→)B. What; whom
C. It; whose
D. As; whom
解析：通过分析句子结构，可知这个句子中包含一个主语从句，和一个非限制性定语从句。且引导词在主语从句中作主语，表示“什么”的含义，故用what。介词 + 关系代词引导的定语从句，指人只能用whom。