A traditional farming system in the coastal region of Karnataka that combines fish farming with agriculture:

Aquaculture
Pokkali farming
Mixed farming
Terrace farming

The correct answer is: A) Aquaculture

Aquaculture is the farming of aquatic organisms, including fish, crustaceans, mollusks, and aquatic plants. Aquaculture can be done in both marine and freshwater environments.

Pokkali farming is a traditional farming system in the coastal region of Karnataka that combines fish farming with agriculture. In pokkali farming, rice is grown in flooded fields during the monsoon season. After the rice harvest, the fields are drained and fish are introduced. The fish feed on the rice stubble and other aquatic plants, and their waste fertilizes the rice fields.

Mixed farming is a system of agriculture in which crops and livestock are raised together. Mixed farming can be done on a small scale, such as on a family farm, or on a large scale, such as on a commercial farm.

Terrace farming is a system of agriculture in which crops are grown on terraces that have been built on hillsides. Terrace farming helps to prevent soil erosion and to conserve water.

Aquaculture is the best answer to the question because it is the only option that specifically mentions fish farming. Pokkali farming, mixed farming, and terrace farming are all systems of agriculture that involve raising crops, but they do not specifically mention fish farming.