Final answer:
The closest estimate of the population of South America in 2010 is 4 x 10⁸.
Step-by-step explanation:
The population of South America in 2010 was 383,276,304. To find the closest estimate of this number, we need to look at the answer choices. Option A is 4 x 10⁷, which is 4 multiplied by 10 to the power of 7. Option B is 4 x 10⁸, which is 4 multiplied by 10 to the power of 8. Option C is 3 x 10⁷, which is 3 multiplied by 10 to the power of 7. Option D is 4 x 10⁶, which is 4 multiplied by 10 to the power of 6. Comparing these options to the actual population of South America, the closest estimate is Option B, 4 x 10⁸.