Correct Answer: Option A) 1 and 2 only
The Ganga river system primarily influences two of the mentioned plains:
Punjab-Haryana Plain: This region is influenced by the tributaries of the Ganga system, particularly the Yamuna river which is a major tributary of the Ganga. The rivers flowing through this plain (like Sutlej, Beas, Ravi) eventually join the Indus, but the eastern part of this plain is influenced by the Yamuna river which is part of the Ganga system.
Ganges-Yamuna Plain: This is directly influenced by the Ganga and its major tributary, the Yamuna. This plain forms the core of the Ganga basin and is the most fertile region of the Indo-Gangetic plains due to the alluvial deposits of the Ganga river system.
Brahmaputra Plain: The Brahmaputra has its own distinct river system, separate from the Ganga system. While both the Ganga and Brahmaputra eventually meet in Bangladesh to form the massive Ganga-Brahmaputra delta, the Brahmaputra plain in northeast India (primarily in Assam) is influenced by the Brahmaputra river system, not the Ganga river system.