Concept:Kolkata port is a riverine port located on the River Hooghly, a distributary of the Ganga.Explanation:The port lies on the left bank of the Hooghly River, about 203 km from the sea.It is the only major riverine port in India and has one of the longest navigational channels in the world.The Bhagirathi–Hooghly river system is tidal, allowing large ships to reach the port.The port is not directly on the Bay of Bengal or at Ganga Sagar (Sagar Island).Therefore, the correct location is the River Hooghly.Answer:River Hooghly (Option C)