The correct answer is option 2: Nile. The Nile river is widely recognized as the longest river in the world. It spans over 4,000 miles, flowing through multiple countries including Egypt, Sudan, South Sudan, Uganda, and Ethiopia. The Nile has historically played a crucial role in the development of ancient civilizations, providing a source of water, irrigation, and transportation. It is formed by the confluence of the White Nile and the Blue Nile, and eventually flows into the Mediterranean Sea. The Ganga (option 1) is a major river in India, but it is not the longest. The Brahmaputra (option 3) is also a major river, primarily in India and Bangladesh, but it is not the longest either. The Amazon (option 4) is the largest river by discharge of water, but it is not the longest.