Which one is included among the left-bank tributaries of the Ganga?

Correct answer: Gandak

The direct answer is D, Gandak. To identify a left-bank tributary, imagine facing downstream, in the direction in which the Ganga flows. A tributary joining from the northern side is called a left-bank tributary. Gandak rises in the Himalayan region and joins the Ganga from the north, so it is a left-bank tributary. Son joins the Ganga from the south and is a right-bank tributary. Chambal is a tributary of the Yamuna, not a direct left-bank tributary of the Ganga. Betwa also joins the Yamuna, so it is not the required answer. Gandak is therefore correct. Ghaghara and Kosi are also commonly remembered with Gandak as important northern or left-bank tributaries, but they are not options here. Exam cue: when facing downstream, north is generally on the left in this stretch of the Ganga.