While the presence of rats in homes may cause anxiety and annoyance, they rarely result in driving out the residents. But is exactly what happened to the inhabitants of the 10squaremile Hawadax Island off the coast of Alaska, almost 230 years ago. Now thanks to a fiveyear effort by scientists, the terribly silent "Rat Island" as it had been called for many years has been returned to its rightful owners ----birds! Hawadax Island is part of a chain of volcanic islands in the Bering Sea called the Aleutian Islands. The rats that arrived there in 1780, when a Japanese ship carrying them broke down nearby, completely destroyed the native population because the environment of the island was not built to defend its animals from these predators. There isn't any tree on the Island, which meant that the birds were accustomed to building their nests low in the ground, giving the rodents  easy access to both eggs and baby chicks. As years passed, the birds that had called the island home for thousands of years became endangered and eventually, disappeared completely. In 2007, the U.S. FWS (Fish and Wildlife Service) started a serious plan to rid the island of the rats and try bringing back the beautiful birds that had once called it home. Given that there were an estimated 10,000 rodents inhabiting "Rat Island" and the fact that they reproduce rapidly, it was not an easy task. But by 2009, the Island was officially declared rat free! Then slowly but surely, the birds began to return. Unfortunately, some of the pioneers were unintentionally killed from the leavings of the raticide, a poison that had been used to wipe out the rodents. But now it seems things are becoming more stable and the Island is starting to increasingly look like its former self. Before the transformation, "Hawadax", also known as "Rat Island", was a silent and ghostly place with bird bones, snail remains and rocks covered in rat feces . Today, birds' singing and flying in and out is a common sight. Tufted puffins and song sparrows, which had long disappeared, are gradually making their way back. Scientists have also been observing an increase in ground nesting and shorebirds. Though the Island is still not back to its full glory, the signs are encouraging and things can only get better, as time passes. From the passage, we can know the plan of US FWS    _   .
has helped the island fully recovered cost little but benefited greatly involved poisoning the rats on a large scale accomplished its goal after exactly 24 months
Question: While the presence of rats in homes may cause anxiety and annoyance, they rarely result in driving out the residents. But is exactly what happened to the inhabitants of the 10squaremile Hawadax Island off the coast of Alaska, almost 230 years ago. Now thanks to a fiveyear effort by scientists, the terribly silent "Rat Island" as it had been called for many years has been returned to its rightful owners ----birds! Hawadax Island is part of a chain of volcanic islands in the Bering Sea called the Aleutian Islands. The rats that arrived there in 1780, when a Japanese ship carrying them broke down nearby, completely destroyed the native population because the environment of the island was not built to defend its animals from these predators. There isn't any tree on the Island, which meant that the birds were accustomed to building their nests low in the ground, giving the rodents  easy access to both eggs and baby chicks. As years passed, the birds that had called the island home for thousands of years became endangered and eventually, disappeared completely. In 2007, the U.S. FWS (Fish and Wildlife Service) started a serious plan to rid the island of the rats and try bringing back the beautiful birds that had once called it home. Given that there were an estimated 10,000 rodents inhabiting "Rat Island" and the fact that they reproduce rapidly, it was not an easy task. But by 2009, the Island was officially declared rat free! Then slowly but surely, the birds began to return. Unfortunately, some of the pioneers were unintentionally killed from the leavings of the raticide, a poison that had been used to wipe out the rodents. But now it seems things are becoming more stable and the Island is starting to increasingly look like its former self. Before the transformation, "Hawadax", also known as "Rat Island", was a silent and ghostly place with bird bones, snail remains and rocks covered in rat feces . Today, birds' singing and flying in and out is a common sight. Tufted puffins and song sparrows, which had long disappeared, are gradually making their way back. Scientists have also been observing an increase in ground nesting and shorebirds. Though the Island is still not back to its full glory, the signs are encouraging and things can only get better, as time passes. From the passage, we can know the plan of US FWS    _   .
A. has helped the island fully recovered
B. cost little but benefited greatly
C. involved poisoning the rats on a large scale
D. accomplished its goal after exactly 24 months
Answer: