Choose the best words into the sentences. Sudan is the only male northern white rhino (犀牛) left in the world. That (mean) Sudan, 42, is the last hope for avoiding extinction. (protect) him, officials have placed him under 24-hour armed guard at the OI Pejeta Conservancy in central Kenya. Sudan lives there two female northern white rhinos, Fatu and Najin. Northern white rhinos, can weigh up to 5,000 pounds, were once plentiful across northern and central Africa. (hunter) have killed thousands of rhinos because of high demand for the animals，horns (角). Rhino horns, believed to have medical effects, are used in (tradition) Asian medicines. More than 1,000 rhinos (kill) in 2014 in South Africa alone and fifty-four rhinos in Kenya, which has a much (small) population. Sudan, Fatu, and Najin have had their horns (remove) so that they will not be hunted. People hope Sudan and one of the females will be able to have a baby. Sudan is very old, but scientists will not give up hope.