Explanation:

• Kosi River drains the northern slopes of the Himalayas in the Tibet Autonomous Region and the southern slopes in Nepal before entering India.
• It is also known as Saptakoshi for its seven upper tributaries. These include the Tamur Koshi, Arun River and Sun Koshi. The Sun Koshi’s tributaries from east to west are Dudh Koshi, Bhote Koshi, Tamba Koshi and Indravati Koshi.
• The Saptakoshi crosses into northern Bihar where it branches into distributaries before joining the Ganges near Kursela in Katihar district.

Hence only statement 2nd is correct.