The correct answer is option 4, the United States of America.

To understand this, let`s start by acknowledging that China and India are the two most populous countries in the world, with China being the most populated and India the second most populated.

Option 1, Brazil, is a populous country in South America, but it is not more populous than China or India. Therefore, it is not the correct answer.

Option 2, Indonesia, is the fourth most populous country in the world. While its population is significant, it is not as populous as China, India, or the United States. Thus, it is not the correct answer.

Option 3, the Russian Federation, is the largest country by land area, but its population is not more than that of China, India, or the United States. Therefore, it is not the correct answer.

Option 4, the United States of America, is the third most populous country in the world. It has a substantial population, but it is still less populous than China and India. However, it is the most populous country among the given options, making it the correct answer.