Measuring more than five feet tall and ten feet long, the Javan rhinoceros is often called the rarest large mammal on earth. Though the habitat of the Javan rhino once extended across southern Asia, now there are fewer than one hundred of the animals in Indonesia and fewer than a dozen in Vietnam. The decline of the species may have progressed too far to be reversed. For centuries, farmers who wished to cultivate the rhino's habitat viewed the animals as crop-eating pests and shot them on sight; during the colonial period, hunters slaughtered thousands for their horns, as poachers still do today. The surviving Vietnamese herd has diminished to the point that it can no longer maintain the genetic variation necessary for long-term survival. The Indonesian herd cannot be used to supplement the Vietnamese population because, in the millions of years since Indonesia separated from the mainland, the two groups have evolved into separate sub-species. The Indonesian rhinos are protected on the Ujung Kulon peninsula, which is unsettled by humans, and still thought to have sufficient genetic diversity to survive. The lack of human disturbance, however, allows mature forests to replace the shrubby vegetation preferred by the animals. Human benevolence may prove little better for these rhinos than past human maltreatment.

The primary purpose of the passage is to

a) discuss the habitats of endangered species in Southern Asia
b) describe the ways in which human actions affect the viability of endangered species
c) outline the decay of a particular species
d) compare and contrast two related sub-species
e) advocate measures designed to aid a particular species