哪儿 nǎ ér is used in rhetorical questions to convey a more contentious enquiry before a noun (with 的 de), verb or adjective:
这是哪儿的话？
Zhè shì nǎ ér de huà ？
What sort of talk is that/this? (derogatory)/Don’t mention it. (polite)
我哪儿吃得下呢？
Wǒ nǎ ér chī dé xià ne ？
How (on earth) can I eat it/any more?
我的话哪儿错了？
Wǒ de huà nǎ ér cuò le ？
What (on earth) is wrong with what I said?
[1] Yip, P. C., Rimmington, D., Xiaoming, Z., & Henson, R. (2009). Basic Chinese: a grammar and workbook. Taylor & Francis.
