Answer:
The three statements that support the idea that South America is a single cultural region are as below:
In most Latin American countries, the majority of locals speak Spanish.
The "Mardi Gras tradition" is celebrated with "grand parades" in Brazil, Colombia, Argentina and Uruguay.
Many people in Argentina, Chile, Peru and Ecuador practice Roman Catholicism.
Explanation:
Countries like Argentina, Bolivia, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay, and Venezuela are Spanish speaking countries.
The festival of El Carnaval is celebrated in most South American countries.
The tradition of Mardi Gras is a part of El Carnaval. 69% of the total "South American population" practices Roman Catholicism.