Hello there!
Your answer would be B). The Line of Demarcation
The reason why the Line of Demarcation would be the correct answer is because the Line of Demarcation was part of a treaty that assigned areas for Spain and Portugal to develop. The line was also known as a restriction for the amount of land Spain and Portugal could get. Most of the Eastern side of South America was claimed by Portugal because of the Line of Demarcation. The land that was claimed by Portugal would be now known as Brazil. The Line of Demarcation really shaped the linguistic, or language, of the regions in South America because if it wasn't for the Line of Demarcation, South America would've developed a lot differently, and would probably be different today.