Which tributary of the Ganga is especially known for floods?

Correct answer: Kosi

The direct answer is C: Kosi. The Kosi is a major tributary of the Ganga and is especially famous for serious floods in northern Bihar. It carries large amounts of sediment, and its channel has historically shifted, so floodwater can spread widely over the surrounding plains. Option C is correct because flood risk and changing course are key textbook associations of the Kosi. Option A, Son, is also a Ganga tributary but is not the specially noted answer for this flood association. Option B, Chambal, joins the Yamuna system and is not usually identified in this question as the Ganga tributary famous for floods. Option D, Betwa, also joins the Yamuna and is not the intended river. The answer must be chosen by the strongest textbook clue, not merely by asking whether a river can ever flood. Memory cue: “Kosi” is commonly remembered as the “sorrow of Bihar” because of its destructive floods and shifting course.