Answer:
1. Córdoba 2. peso argentino 3. Buenos Aires 4.europeo
Step-by-step explanation:
1. Córdoba is in size the second city of Argentina
2. No South American country would voluntary use the american dollar as a national currency and ¨el colón¨ sounds pretty strange
3. Buenos Aires is the only name of the 4 that possibly could have 13 million people
4. I would say that Argentina is definitely the most european country in South America because that´s what they always would like to be known for
The other 3 possibilities of question 4 depend very rmuch on personal views and/or are impossible or hard to to measure, like democracy for example.