A is most likely right because a lot modern European countries get their borders from cultural and linguistic boundaries after old empires like Austria-Hungary, Russia, and Germany split up. Poland, Czechoslovakia, and Slovenia, just to name a few, were ethnic groups without countries before WW1.
B: isn't true, just look at eastern Europe in the 17th century, tons of ethnic groups living in one country. Even with more immigration to the Europe, most immigrants assimilate into European cultures.
C: Although geography can influence political borders to varying degrees, European nations don't strictly follow physical geographic features to my knowledge. There are a lot of borders based off of rivers you can see have stayed the same despite the rivers moving (Serbia and Croatia's border is a prime example)
D: I don't know what 'define' means in this context, but if it means religion and geography are the main reasons Europe get's their borders is just flat out wrong. We already talked about geography, but religion doesn't effect European borders since most European countries are christians and are secular. The only example I can think off the top of my head of religion affecting borders is in Ireland when they separated the protestant north from the rest of the island which was catholic.
Hope this helped you out :)
<span>Great Britain did no receive any land in Europes mainland during the Congress of Vienna. The country did however, receive considerable holdings in the new colonies. The rest of the nations in the Congress of Vienna, received at least some portion of land in Europe.</span>
This is known in history as the Civil Rights Act of 1866 where a coalition was formed by both moderate and radical republicans. In such act, it made African Americans citizens of the United States of America, including the total elimination of discrimination against African Americans.
The answer for your question is Spain
I think the answer is A, it's the one that makes the most sense
