The role of a keystone species is.. A. To kill off invasive species in the area
B. To maintain biodiversity in the ecosystem through complex interactions with other animals in the area
C. To be able to make the environment safe

The answer is B

Explanation:

A keystone species is an organism that helps define an entire ecosystem. Without its keystone species, the ecosystem would be dramatically different or cease to exist altogether. The ecosystem would be forced to radically change, allowing new and possibly invasive species to populate the habitat.

answer: 20 percent

the fish culture has become a developing commercial practice in developing countries which is already prominent in developed countries of the world. the major fish protein demand is being supplemented in developing countries is   fishing to meet the needs of the growing population. therefore, in some developing nations, the percentage of animal protein from fish in the diet can be as high as 20 percent.