RAS question
The Son River is a tributary of:
Correct answer: (B) Ganga.
The Son River is a major right-bank tributary of the Ganga.
Explanation
The Son River belongs with the Ganga system, not the peninsular river systems named in the other options. It originates near Amarkantak in Madhya Pradesh, the same broad area associated with the Narmada, but its course is different: it flows north-east and joins the Ganga near Patna. The official Central Water Commission page on the Ganga basin lists the Son among the important tributaries of the Ganga. That is why the correct association is Ganga, even though the Amarkantak origin can tempt a comparison with the Narmada. The key exam hook is basin membership, not just source region.
Why the other options are wrong
- (A) Godavari is wrong because the Son is identified with the Ganga basin and flows north-east to join the Ganga near Patna.
- (C) Yamuna is wrong because the CWC lists both the Yamuna and the Son as important tributaries of the Ganga, not one as a tributary of the other.
- (D) Narmada is wrong because sharing the Amarkantak region does not decide the river system; the Son flows north-east to the Ganga, unlike the Narmada.
Concept
This tests drainage-system classification in Indian geography: source region, direction of flow and confluence must be read together. RAS repeatedly asks such river-basin links because nearby origins and similarly named regional features often mislead candidates.