Which one of the following rivers joins Ganga directly?

The Son (or Sone) river is a major right-bank tributary of the Ganga that originates in the Amarkantak plateau and joins the Ganga directly near Patna, Bihar [2]. In contrast, the Chambal, Betwa, and Ken rivers are primary tributaries of the Yamuna river [1]. While these rivers are part of the larger Ganga drainage basin, they do not merge with the Ganga directly; instead, they flow northward from the Peninsular highlands to join the Yamuna [5]. The Yamuna itself then travels approximately 1,376 kilometers before its confluence with the Ganga at Prayagraj (Allahabad) [6]. Therefore, among the given options, only the Son river maintains a direct confluence with the main stem of the Ganga.

Sources

1. [1] INDIA PHYSICAL ENVIRONMENT, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Drainage System > Do you Know? > p. 22
2. [2] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 4: Climate of India > 1. The Ganga River Basin > p. 47
3. [3] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 3: The Drainage System of India > The Yamuna River > p. 13
4. [4] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 3: The Drainage System of India > 1.2 Subsequent Rivers > p. 1
5. [5] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 16: Fluvial Landforms and Cycle of Erosion > Subsequent Rivers > p. 210
6. [6] http://dda.gov.in/land-/Journey-Of-Yamuna