In HSK5级 应试指南 (pages 68 and 69), there's an exercise about Confucius (孔子). Two children are arguing about whether or not the sun is closer to the earth during the day. Confucius doesn't know how to answer, and from there...
……
孔子听了他们的话,一时也不知道应该怎么回答。
两个小孩儿笑着说:“[blank]?”
The choices for the blank are:
A. 你说的对吗
B. 太阳离我们有多远
C. 为什么你这么聪明呢 (✗)
D. 谁说你的知识很丰富呢 (✓)
The 笑着 indicates humor is involved in the answer. B is not a joke, so it's incorrect. A is like a genuine question, which is not correct since 孔子 didn't say anything.
I thought the answer was C. 为什么你这么聪明呢 = "Why are you so smart?". This reminds me of a typical joke where there is a group of people together without any of them speaking, and someone might ironically remark "Gee, don't all speak at once!" And indeed, a sign of intelligence is not claiming to know an answer when you don't.
However, the answer is D. 谁说你的知识很丰富呢 = "Who says you have plentiful knowledge?" To me, this sounds like a flat-out insult (claiming 孔子 is not as smart as people say), and not humorous.
The books explanation is as follows:
第52题根据全文判断,孔子回答不了两个小孩子的问题,“两个小孩子笑着说”应该是一种否定的意思,因此选择反问句”D. 谁说你的知识很丰富呢“。
But it seems C, when said jokingly in the given context, also has a 否定的意思. There seems to be something here about Chinese-style humor I'm missing.
Question: Why do the students joke 谁说你的知识很丰富呢 and not 为什么你这么聪明呢?