Question

saving the rhinos
poachers in africa are killing large numbers of rhinos for their horns. rhinoceros horns, valued for use in traditional medicines in vietnam and china, can fetch as much as thirty - six thousand dollars a pound. officials have tried to protect the rhinos: they have created fenced areas for the animals, patrolled their habitats, and even tried removing their horns. despite these efforts, the number of rhinos in africa has been dwindling. one creative solution to the poaching problem is to remove the rhinos from africa altogether. ray dearlove, the founder of the australian rhino project, came up with a plan to relocate eighty rhinos to a safari park outside adelaide, australia, where a breeding herd can be established.
what is the main, or central, idea of the passage?
officials have tried to protect african rhinos from poachers by guarding their habitats and removing their horns, but their efforts have been largely unsuccessful.
because other attempts to protect african rhinos from poachers have failed, the australian rhino project is relocating the rhinos to australia.

Explanation:

The passage first presents the problem of African rhinos being killed by poachers. It then mentions official protection efforts (creating fenced areas, patrolling habitats, removing horns) that have been unsuccessful as the rhino number is dwindling. Finally, it introduces a new solution - the Australian Rhino Project's plan to relocate rhinos to Australia. The second option encompasses the problem (other protection failures) and the new solution (relocating to Australia), which is the main idea. The first option only focuses on the failed protection efforts without the new solution which is a key part of the passage.

Answer:

Because other attempts to protect African rhinos from poachers have failed, the Australian Rhino Project is relocating the rhinos to Australia.