Explanation: Port cities are urban centers that are strategically located on the coast or along major rivers, serving as hubs for maritime trade and transportation. These cities are crucial for the economic development of a country, as they facilitate the import and export of goods through sea routes. The significance of port cities lies in their ability to connect a country with international markets, thereby boosting trade and commerce.
In the context of India, Chennai and Vishakapatnam are well-known port cities. Chennai, located on the southeastern coast of India, is a major economic hub and plays a significant role in the country's maritime trade. It is one of the largest ports in India and handles a substantial volume of cargo, including automobiles, petroleum products, and general cargo. The port of Chennai is also a key player in the country's automobile industry, with several major automobile manufacturers having their manufacturing units in the vicinity.
Vishakapatnam, located on the eastern coast of India, is another major port city. It is an important center for maritime trade and has a significant role in the economic development of the region. The port of Vishakapatnam handles a variety of cargo, including coal, iron ore, and other minerals. It is also a major center for the fishing industry and has a significant role in the export of seafood.
On the other hand, Delhi is an inland city and not a port city. It is the capital of India and is located far from the coast, making it unsuitable for maritime trade. Delhi is a major economic and political center, but its location does not allow it to function as a port city.
In conclusion, Chennai and Vishakapatnam are well-known port cities in India, while Delhi is not. The correct answer is (D) Only (A) & (B), as it correctly identifies Chennai and Vishakapatnam as port cities and excludes Delhi, which is not a port city.