Important ports of Karnataka and Kerala are Mangalore and Kochi.

Mangalore Port:
- Mangalore port is located in Mangalore, Karnataka.
- It is one of the major ports in India and is known for its natural harbor.
- The port handles a variety of cargo including petroleum products, chemicals, fertilizers, edible oils, and food grains.
- It has specialized facilities for handling liquid cargo, bulk cargo, and container cargo.
- The port is well-connected to major cities in India through road and rail networks.
- It plays a significant role in the export and import trade of Karnataka.

Kochi Port:
- Kochi port is located in Kochi, Kerala.
- It is one of the largest ports in India and is often referred to as the "Queen of the Arabian Sea".
- The port is strategically located on the west coast of India and serves as a gateway for international trade.
- It handles various types of cargo including containers, bulk cargo, and liquid cargo.
- Kochi port is a major center for seafood exports and also caters to the needs of the oil refineries in the region.
- The port has modern facilities and is well-connected to major cities in India and international destinations.

Reason for the correct answer:
- The correct answer is option 'D' because both Mangalore and Kochi are important ports in Karnataka and Kerala respectively.
- Chennai, on the other hand, is a port city in Tamil Nadu and not in Karnataka or Kerala.
- Therefore, options 'a' and 'c' are incorrect.
- Option 'b' is incorrect because Mangalore is a port in Karnataka and not in Kerala.
- Only option 'D' includes both Mangalore and Kochi, which are the important ports of Karnataka and Kerala respectively.