The correct answer is D. Punpun.
The Punpun is a river in India that flows through the states of Bihar and Jharkhand. It is a tributary of the Ganges River. The Punpun originates in the hills of Jharkhand and flows northwards through the plains of Bihar. It joins the Ganges River near Patna. The Punpun is a seasonal river and its flow varies greatly throughout the year. It is a major source of irrigation for the region.
The Saryu is a river in India that flows through the states of Uttar Pradesh and Uttarakhand. It is a tributary of the Ganges River. The Saryu originates in the Garhwal Himalayas and flows eastwards through the plains of Uttar Pradesh. It joins the Ganges River near Allahabad. The Saryu is a major source of irrigation for the region.
The Son is a river in India that flows through the states of Madhya Pradesh, Chhattisgarh, Jharkhand, and Bihar. It is a tributary of the Ganges River. The Son originates in the Amarkantak hills of Madhya Pradesh and flows eastwards through the plains of Chhattisgarh and Jharkhand. It joins the Ganges River near Patna. The Son is a major source of irrigation for the region.
The Kiul is a river in India that flows through the state of Bihar. It is a tributary of the Ganges River. The Kiul originates in the hills of Jharkhand and flows northwards through the plains of Bihar. It joins the Ganges River near Patna. The Kiul is a major source of irrigation for the region.
Therefore, the only river among the given options that does not enter the Ganges from the south is the Punpun.