Are 这是哪 and 这是在哪 different questions?
&quot;这是哪？&quot; short for &quot;这是哪里？&quot;; It means  &quot;where is this place/ what place it is?&quot; (you want to know the name of a place)

Example:

A and B are at a park,
A asks B: &quot;这是哪(里)?&quot; - &quot;where is this place?&quot;
B answers: &quot;这是佛光山公园&quot; - &quot;This is Buddha Light Mountain Park&quot;
It would be easier to understand if you say &quot;这是什么地方&quot; instead of &quot;这是哪？&quot;


&quot;这是在哪？&quot; short for &quot;这是在哪里？&quot; It means &quot;where it is at?&quot; (you want to know where an object is located or where an event took place)

Example:

A pointing at a poster and asks B
A: &quot;佛光山公园？ 这是在哪？&quot; - &quot;Buddha Light Mountain Park? Where is it located?&quot;
B: &quot;佛光山公园当然在佛光山&quot; - &quot;Buddha Light Mountain Park is in Buddha Light  Mountain of course&quot;
A: &quot;不，我的意思是佛光山公园在哪个城市&quot; - &quot;No, I meant Buddha Light Mountain Park is in which city&quot;

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&quot;曹操刚跟呂布战斗？这是在哪(里发生的)？&quot; - &quot;Cao Cao just fought with Lu Bu? Where was it (took place)?&quot;