Which of the following is an example for the most important cause that is driving the flora and the fauna to extinction?

Among the 4 causes for biodiversity loss, habitat loss and fragmentation is the most important one. Clearing of amazon rain forests for the soya bean cultivation and the grazing of animals is an example for this.

Introduction of Nile perch into Lake Victoria : Alien species invasion.

Presence of water hyacinth in the Indian ponds and lakes : Alien species invasion.

Extinction of passenger pigeon and Steller's sea cow : Over-exploitation.