Amarkantak lies on the Maikal range — option 4.

Why the place is remarkable. Amarkantak, in the Anuppur district of Madhya Pradesh, stands at about 1,050 metres where the Vindhya and Satpura ranges meet along the Maikal hills. It is the source of three rivers that then flow in three different directions :

A single hill that feeds both the Arabian Sea and the Bay of Bengal is a true continental divide, and Amarkantak is treated as a sacred place partly for that reason.

Why the Son matters in Bihar. It enters the state from the south, waters the Rohtas and Bhojpur country through the Sone canal system — one of the oldest large irrigation works in India, begun in the 1870s at Dehri-on-Sone — and joins the Ganga just west of Patna. It is one of the south-bank rivers of Bihar: seasonal, rain-fed, with a wide sandy bed, quite unlike the silt-laden Himalayan rivers of the north bank.

Distinguishing the other options. The Rajmahal hills are in Jharkhand, where the Ganga turns south — the country of the Santhal hool. The Mahadeo hills are part of the Satpura system in Madhya Pradesh, around Pachmarhi. Makalu is the odd one out entirely — it is the fifth highest mountain in the world, on the Nepal-Tibet border, and has nothing to do with peninsular India; its similarity to “Maikal” is exactly what the question exploits.

Hence, the answer is the Maikal range.