题目材料
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.
According to the passage, which of the following best explains why the number of Javan rhinos in Vietnam cannot be increased by additions from those in the Ujung Kulon peninsula?
- AThe two species of Javan rhino constitute distinct sub-species.
- BThe land area where the Indonesian rhinos live is physically separated from the land area where the Vietnamese rhinos live.
- CThe absence of humans on the Ujong Kulon peninsula makes it difficult to capture the Indonesian rhinos.
- DThere are too few Vietnamese rhinos remaining to provide the genetic variation necessary to maintain a healthy population.
- EA combination of human maltreatment and neglect will prevent the rhino population from recovering.
显示答案
正确答案: A