The correct answer is: 1, 2, 4.
The rivers Gandak, Son, and Punpun merge into the Ganges in Bihar.
The Gandak is a river in Nepal and India. It is a tributary of the Ganges River. The Gandak River originates in the Himalayas in Nepal. It flows through the Indian states of Uttar Pradesh and Bihar. The Gandak River joins the Ganges River near Patna, Bihar.
The Son is a river in India. It is a tributary of the Ganges River. The Son River originates in the Kaimur Range in the Indian state of Bihar. It flows through the Indian states of Bihar, Jharkhand, and Madhya Pradesh. The Son River joins the Ganges River near Patna, Bihar.
The Punpun is a river in India. It is a tributary of the Ganges River. The Punpun River originates in the Kaimur Range in the Indian state of Bihar. It flows through the Indian states of Bihar and Jharkhand. The Punpun River joins the Ganges River near Patna, Bihar.