Which tributary of the Son river flows almost entirely outside Uttar Pradesh and enters the state on

Q. Which tributary of the Son river flows almost entirely outside Uttar Pradesh and enters the state only just before its confluence with the Son?
Answer: Kanhar
Notes: Kanhar originates in Chhattisgarh, traverses Jharkhand, and enters Uttar Pradesh near its confluence with the Son river in Sonbhadra district.