The correct option is (a).
Explanation
The Yamuna is the longest and the westernmost tributary of the Ganga river system. It is a major component of the Himalayan drainage network.
- Statement 1 is correct: The river Yamuna originates from the Yamunotri Glacier on the western slopes of the Banderpunch range (6,316 m) in the Uttarakhand Himalayas.
- Statement 2 is incorrect: The Yamuna does not flow perpendicular to the Ganga. Instead, it flows parallel to the Ganga for a significant distance across the plains before merging with it.
- Statement 3 is incorrect: The Yamuna joins the Ganga at Prayagraj (formerly Allahabad). This confluence is known as the Triveni Sangam. Haridwar is the location where the river Ganga descends from the mountains into the plains.
Key Takeaway: The Yamuna rises from the Yamunotri Glacier, flows parallel to the Ganga, and meets it at Prayagraj, serving as the largest tributary of the Ganga system.