哪儿 / 哪里【nǎr / nǎlǐ】

哪儿 and 哪里 both ask "where", and they sit where the place would sit.

哪儿 is northern and 哪里 southern; in writing either is fine and neither is more formal.

Asking where an action happens

The question word goes with 在 in front of the verb, not after it. nǐ你gōng zuò工作zài在nǎ r5哪儿 is wrong.

The answer keeps the slot

这儿 and 那儿 are the answers

这儿 for here, 那儿 for there, with 这里 and 那里 as the southern forms.

哪儿 as "anywhere" and "nowhere"

With 都 or 也 it stops asking: 哪儿都去过 means "has been everywhere", 哪儿都不去 means "isn't going anywhere".