71. A passage is given with 5 questions following it. Read the passage carefully and choose the best answer out of the four alternatives.
Rhino poaching in Assam is one of the major environmental issues in India which continues in the region of Kaziranga National Park, Manas National Park and some other grasslands of Assam. The one horn rhino or Indian rhino is surviving in the north-east corner of India, Assam. Kaziranga National Park, Pobitora in Marigaon district and Orang National Park in Darrang district of Assam account almost 95% of the total wild one horned rhino in the world. These rhinos inhabit most of the floodplains of the Indogangetic and Brahmaputra riverine tracts and the neighboring foothills.
Sport hunting became common in the late 1800s and early 1900s.Indian rhinos were hunted relentlessly and persistently. Reports from the middle of the 19th century claim that some military officers in Assam individually shot more than 200 rhinos. By 1908, the population in Kaziranga had decreased to around 12 individuals.In the early 1900s, the species had declined to near extinction.
Poaching for rhinoceros horn became the single most important reason for the decline of the Indian rhino after conservation measures were put in place from the beginning of the 20th century, when legal hunting ended. From 1980 to 1993, 692 rhinos were poached in India. In India's Laokhowa Wildlife Sanctuary 41 rhinos were killed in 1983, virtually the entire population of the sanctuary. By the mid-1990s, poaching had rendered the species extinct there.
Illegal rhino horn trade has been the main problem facing managers of the rhino-protected areas of Assam. Some other parts like nails, skins have very high value in Asian traditional medicinal market. According to research by Traffic (conservation programme) and World Wide Fund for Nature, some Vietnamese buyers believe horn to be a cure for cancer when ground to a fine powder. According to a survey conducted by World Wide Fund for Nature in South Africa, it is kept by wealthy people in Vietnam as a "peace of mind" cure.
In 1993, rhino horn was removed from the official lists of Traditional Chinese Medicine. It is now only sold in Vietnam following an unsubstantiated rumour that horn cured a high-ranking official in Vietnam of cancer.
According to the passage, what is the main problem plaguing rhino conservation?