The phrase "about which nation" is correct and usable in written English.
It can be used when discussing a specific nation in a context where the subject of the discussion is related to that nation.
Example: "The report provides insights about which nation has the highest levels of pollution."
Alternatives: "regarding which country" or "concerning which nation".
There was no doubt about which nation prevailed Wednesday night.
There was much polite sparring about which nation had behaved worse in the long history of animosity between the two nations.
Wales and Serbia will both have plenty to say about which nation qualifies automatically for Russia but finishing 2016 with 10 points from the 12 available has left O'Neill's team full of belief.
When Gallup posed an open-ended question in February about which nation was the United States' leading enemy, China was second only to Iran and was seen as far more worrisome than the rest of the top five put together — North Korea, Afghanistan and Iraq.
With players from Canada (both French and English) to go with those from the United States, Sweden, Finland, Russia, the Czech Republic, Slovakia, Latvia, Germany, Norway and elsewhere, some N.H.L. dressing rooms can include conversations in a half-dozen languages, occasionally arguing about which nation has the best players.
In this manner, the operational concern about which nation's bonds to buy is alleviated.
There is much debate about who will lead the medal count in London, but virtually none about which nations will be in the top three.
Second, his declaration of the atmosphere as a common good, owned by all for all, may help settle the enduring argument about which nations have the responsibility to act.
But at the press conference, Mardini was more interested in talking about swimming than politics, insisting that which nation she swims for was not important.
"Which nation?" retorts Gerard.
