单选题 This is one of the most beautiful songs ______I have ever heard.
A. what B. which C. that D. as

【正确答案】 C
【答案解析】本题考查引导定语从句的关系代词。当先行词为物时，引导词可以使用which或that，但是当先行词前面有形容词的最高级修饰时，只能用that。