Which river forms the Ganga plain?

The Ganga Plain is formed by the Ganga River and its tributaries. The river originates from the Himalayas and flows through northern India, creating a vast alluvial plain as it deposits fertile soil along its path. This plain is one of the most fertile and densely populated regions of India. The Ganga River, along with its tributaries like the Yamuna, Ganges, and Brahmaputra, provides water for agriculture and sustains millions of people living in the region. The plain is vital for farming, and its rich soil supports the growth of various crops.

This question related to Chapter 3 Social Science Class 6th NCERT.
From the Chapter 3. Landforms and Life.
Give answer according to your understanding.