Correct Answer: Ghaghara
Subject: 2025
Explanation: <p><strong>Key Fact:</strong> The Sarayu River is another name for the lower/middle course of the Ghaghara River, particularly as it flows past the holy city of Ayodhya in Uttar Pradesh.</p><p><strong>Additional Info:</strong> Originating near Lake Manasarovar in Tibet from the Mapchachungo glacier, the river is known as the Karnali in Nepal. After descending into the northern plains of India, it is referred to as the Ghaghara and Sarayu. It is a major left-bank tributary of the Ganga, joining it near Revelganj in Chhapra, Bihar.</p><p><strong>Why the other options are wrong:</strong> The Son is a major right-bank tributary originating from the Amarkantak plateau; the Kosi originates in Tibet/Nepal and is known as the 'Sorrow of Bihar'; the Kali (Sharda) forms the western boundary between India and Nepal before joining the Ghaghara.</p><p><strong>Exam Trick:</strong> Sarayu = Ghaghara (Ayodhya sits right on its banks).</p><p><strong>Final Answer:</strong> Ghaghara</p>