At which one of the following places do two important rivers of India originate; while one of them flows towards north and merges with another important river flowing towards Bay of Bengal, the other one flows towards Arabian Sea?

Answer: (a) Amarkantak

Amarkantak is the source of the Son (flows north into the Ganga) and the Narmada (flows west to the Arabian Sea).

The idea

A watershed is an upland divide separating neighbouring drainage basins. Rivers beginning close together can descend opposite sides and reach different seas. Use both the source region and the later drainage direction; a common source does not imply a common mouth.

Amarkantak upland → Drainage divides around the source region → Narmada descends west → Son descends towards the northern plain → Son joins the Ganga → Their waters reach different seas

Why the others are wrong

(b) Badrinath is on the Alaknanda — no west-flowing river.

(c) Mahabaleshwar is the source of the Krishna (east).

(d) Nasik (Trimbak) is the source of the Godavari (east).

The trap

The Mahanadi also starts near here (Sihawa), but it flows east directly to the Bay.

Also know

Johila is another river associated with Amarkantak and joins the Son system. Tapi starts near Multai, not Amarkantak. Krishna begins near Mahabaleshwar and Godavari near Trimbak; Mahanadi’s source is near Sihawa. Keep each plateau source with its own basin.