参考答案：C

解析： 本题考查交际用语。当对方表示感谢时，常用的答语有：You're welcome./That's all right./It's a pleasure./It's my pleasure./That's nothing./It was no trouble at all. 等。八项意思为“乐于效劳”；D项表示同意等；B项“不要紧，没关系”。故选C。