The German shepherd runs off and noses around in the grass of Kenya's Laikipia Plateau. "OK, Oakley," the dog's handler orders, "Find it!" Oakley sniffs   until he comes to a bush, then stops, sits, and looks up at his handler. She bends to see what he has found: the waste of an endangered African wild dog. "Good dog!" she praises. The handler pulls a tennis ball from her pocket. Oakley jumps for his reward. "He doesn't actually want the waste," says Aimee Hurt, a founding member of the U.S.-based group Working Dogs for Conservation. Hurt is in Kenya to train both Oakley and his handler. "He finds it so he can play with his ball. We're the ones who want the waste." Detection dogs are sometimes taught to locate actual animals. Black-footed ferrets   have been studied with their help. But more often the dogs learn to locate the waste of creatures such as bears, wolves and mountain lions. What the dogs find provides scientists with data about a species. Scientists can use the DNA collected from animal waste to identify individuals, sex, and population sizes -- all without ever seeing the animal itself. "It can take years to gather this kind of information if you have to trap animals," Hurt explains. Waste analysis might make a huge difference when wild species are accused of attacking domestic livestock  . Hurt says, "A good detection dog will find the waste so we can see what the animal is actually eating." This may help reduce problems between people and wildlife. What is the main idea of the passage?
Detection dogs can help scientists study wildlife. Detection dogs can defend wildlife. Detection dogs can help the police catch the criminals. Detection dogs can help local people defend domestic livestock.
Question: The German shepherd runs off and noses around in the grass of Kenya's Laikipia Plateau. "OK, Oakley," the dog's handler orders, "Find it!" Oakley sniffs   until he comes to a bush, then stops, sits, and looks up at his handler. She bends to see what he has found: the waste of an endangered African wild dog. "Good dog!" she praises. The handler pulls a tennis ball from her pocket. Oakley jumps for his reward. "He doesn't actually want the waste," says Aimee Hurt, a founding member of the U.S.-based group Working Dogs for Conservation. Hurt is in Kenya to train both Oakley and his handler. "He finds it so he can play with his ball. We're the ones who want the waste." Detection dogs are sometimes taught to locate actual animals. Black-footed ferrets   have been studied with their help. But more often the dogs learn to locate the waste of creatures such as bears, wolves and mountain lions. What the dogs find provides scientists with data about a species. Scientists can use the DNA collected from animal waste to identify individuals, sex, and population sizes -- all without ever seeing the animal itself. "It can take years to gather this kind of information if you have to trap animals," Hurt explains. Waste analysis might make a huge difference when wild species are accused of attacking domestic livestock  . Hurt says, "A good detection dog will find the waste so we can see what the animal is actually eating." This may help reduce problems between people and wildlife. What is the main idea of the passage?
A. Detection dogs can help scientists study wildlife.
B. Detection dogs can defend wildlife.
C. Detection dogs can help the police catch the criminals.
D. Detection dogs can help local people defend domestic livestock.
Answer: