The correct answer is C. Destruction of habitat.
Habitat destruction is the main reason for the decline of wildlife. When forests are cut down, animals lose their homes and are forced to find new places to live. This can be difficult, and many animals die as a result. Habitat destruction also leads to the fragmentation of ecosystems, which makes it difficult for animals to find food and mates.
Predation is another factor that can contribute to the decline of wildlife. However, predation is usually not the main cause of decline. In fact, predation can actually help to keep populations of animals in check. Hunting is also a factor that can contribute to the decline of wildlife. However, hunting is usually regulated by governments, and it is not the main cause of decline.
In conclusion, the main reason for the decline of wildlife is habitat destruction. This is followed by predation and hunting.