The correct answer is (d). Madgaon is not a natural port/harbour of India. It is a man-made port.
Kochi, Vishakhapatnam, and Chennai are all natural ports. They are located on the coast and have deep water that allows large ships to dock. Madgaon, on the other hand, is located on the Mandovi River. The river is not deep enough for large ships to dock, so Madgaon is a man-made port.
A natural port is a harbor that is formed by the natural features of the land and sea. Natural ports are often located on the coast, where the land meets the sea. They are usually deep enough for large ships to dock, and they often have sheltered waters that protect ships from storms.
A man-made port is a harbor that is created by humans. Man-made ports are often located on rivers or canals. They are usually not as deep as natural ports, and they are not always sheltered from storms. However, man-made ports can be very useful, especially in areas where there are no natural ports.