The answer is China; one-fifth
This is the correct answer. China is the world's most populous nation, with approximately one-fifth of the global population. As of recent estimates, China has a population of over 1.4 billion people, which is roughly 20% of the world's population.
This is incorrect. While China is the most populous country, it does not account for half of the world's population. Half of the world's population would be around 3.9 billion people, which is significantly more than China's population.
This is incorrect. India is the second most populous country, but it does not account for one-third of the world's population. One-third of the world's population would be around 2.6 billion people, which is more than India's current population.
This is incorrect. The United States is not the most populous nation and does not account for one-fifth of the world's population. The U.S. population is around 331 million, which is much less than one-fifth of the global population.
This is incorrect. The United States is not the most populous nation and does not account for half of the world's population. Half of the world's population would be around 3.9 billion people, which is far more than the U.S. population.