Which of the following river systems forms the largest delta system in the world when it enters the Bay of Bengal?

Introduction / Context:
Deltas are landforms created where rivers meet the sea and deposit sediments. Some river systems build very large delta complexes that support millions of people and rich ecosystems. This question asks which river system forms the largest delta system in the world, a fact often highlighted in both Indian and world geography.

Given Data / Assumptions:

• Four major rivers are listed: the Nile, the Ganges Brahmaputra, the Mississippi and the Amazon.
• The focus is on the size of the delta system, not on river length or discharge alone.
• We assume the commonly accepted fact that the Ganges Brahmaputra delta is the world largest delta complex by area.

Concept / Approach:
The Ganges and Brahmaputra rivers, joined by the Meghna in their lower reaches, form a vast, fan shaped delta before entering the Bay of Bengal. This delta extends across eastern India and much of Bangladesh, creating a huge area of low lying, fertile alluvial land. The Sundarbans mangrove forest occupies part of this delta. By contrast, the Nile delta in Egypt, the Mississippi delta in the United States and the Amazon mouth regions are large but do not match the Ganges Brahmaputra system in total delta area according to standard references.

Step-by-Step Solution:
Step 1: Identify that the Ganges and Brahmaputra rivers flow through northern India and Bangladesh and meet near the Bay of Bengal.Step 2: Recall that they carry very large quantities of silt and sediments from the Himalayas and the plains.Step 3: Understand that these sediments are deposited at the mouth of the rivers, forming a wide, low lying delta.Step 4: Recognise that this combined delta is often described as the largest delta in the world in geography texts.Step 5: Therefore, select the Ganges Brahmaputra system as the correct answer.

Verification / Alternative check:
Maps of South Asia clearly show the broad triangular delta region of the Ganges Brahmaputra stretching across a very large area. Many textbooks specifically label it as the world largest delta. In contrast, the Nile delta is smaller and limited to northern Egypt, the Mississippi delta covers a smaller area in the Gulf of Mexico, and the Amazon, despite being massive in discharge, has a more complex estuarine region rather than the largest delta by area. This comparison confirms that the Ganges Brahmaputra system holds the correct title for this question.

Why Other Options Are Wrong:
The Nile in Egypt: Longest river in the world in many references, but its delta is not the largest in area when compared to the Ganges Brahmaputra system.The Mississippi in the United States of America: Has a notable delta around the Gulf of Mexico, but the total area is smaller than the delta formed in the Bay of Bengal.The Amazon in Brazil: Largest river by discharge, with an extensive mouth region, but its delta does not surpass the Ganges Brahmaputra in terms of classic delta area measurement.

Common Pitfalls:
Students may confuse river length or discharge with size of the delta and therefore be tempted to pick the Nile or Amazon. Another mistake is not realising that the Ganges and Brahmaputra together form a joint delta complex, significantly increasing its area. To avoid such errors, it is helpful to learn river superlatives carefully: Nile is often mentioned for length, Amazon for discharge, and Ganges Brahmaputra for largest delta.

Final Answer:
The largest delta system in the world is formed by the Ganges Brahmaputra river system in India and Bangladesh.