With the giant Himalayas caging its towering clouds, the great basi

With the giant Himalayas caging its towering clouds, the great basin where the Brahmaputra merges with the Ganges and Meghna rivers is prone not only to heavy rainfall but also sudden deluges.

A) the great basin where the Brahmaputra merges with the Ganges and Meghna rivers is prone not only to heavy rainfall but also sudden deluges.
B) the great basin in which the Brahmaputra, the Ganges and Meghna rivers merges is prone not only to heavy rainfall but also sudden deluges.
B) the great basin in which the Brahmaputra merges with the Ganges and Meghna rivers, is prone not only to heavy rainfall but also to sudden deluges.
D) the great basin where the Brahmaputra merges with the Ganges and Meghna rivers is prone not only to heavy rainfall but also to sudden deluge.
E) the great basin where the Brahmaputra merges with the Ganges and Meghna rivers is prone not only to heavy rainfall but also to sudden deluges.

Source:
The Economist magazine | Hard hit: A below average monsoon can still prove deadly | Sep 2, 2017