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  3. Ecologists have studied the four chipmunk species that occur on the eastern slope of the Sierra and have learned just how these

Ecologists have studied the four chipmunk species that occur on the eastern slope of the Sierra and have learned just how these

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问题     Ecologists have studied the four chipmunk species that occur on the eastern slope of the Sierra and have learned just how these species interact while remaining separate, each occupying its own elevational zone. The sagebrush chipmunk is found at the lowest elevation, among the sagebrush. The yellow pine chipmunk is common in low to mid-elevations and open conifer forests, including pihon and ponderosa and Jeffrey pine forests. The lodgepole chipmunk is found at higher elevations, among the lodgepoles, firs, and high-elevation pines. The alpine chipmunk is higher still, venturing among the talus slopes, alpine meadows, and high-elevation pines and junipers.Obviously, the ranges of each species overlap.Why don’t sagebrush chipmunks move into the pine zones?Why don’t alpine chipmunks move to lower elevations and share the conifer forests with lodgepole chipmunks?
Look at the four squares[]that indicate where the following sentence can be added to the passage.
Yet each species remains within a fairly well-defined elevational zone.
Where would the sentence best fit?
选项 A、Ecologists have studied the four chipmunk species that occur on the eastern slope of the Sierra and have learned just how these species interact while remaining separate, each occupying its own elevational zone. The sagebrush chipmunk is found at the lowest elevation, among the sagebrush. The yellow pine chipmunk is common in low to mid-elevations and open conifer forests, including pihon and ponderosa and Jeffrey pine forests. The lodgepole chipmunk is found at higher elevations, among the lodgepoles, firs, and high-elevation pines. The alpine chipmunk is higher still, venturing among the talus slopes, alpine meadows, and high-elevation pines and junipers. Yet each species remains within a fairly well-defined elevational zone. Obviously, the ranges of each species overlap.Why don’t sagebrush chipmunks move into the pine zones?Why don’t alpine chipmunks move to lower elevations and share the conifer forests with lodgepole chipmunks?
B、Ecologists have studied the four chipmunk species that occur on the eastern slope of the Sierra and have learned just how these species interact while remaining separate, each occupying its own elevational zone. The sagebrush chipmunk is found at the lowest elevation, among the sagebrush. The yellow pine chipmunk is common in low to mid-elevations and open conifer forests, including pihon and ponderosa and Jeffrey pine forests. The lodgepole chipmunk is found at higher elevations, among the lodgepoles, firs, and high-elevation pines. The alpine chipmunk is higher still, venturing among the talus slopes, alpine meadows, and high-elevation pines and junipers.Obviously, the ranges of each species overlap. Yet each species remains within a fairly well-defined elevational zone. Why don’t sagebrush chipmunks move into the pine zones?Why don’t alpine chipmunks move to lower elevations and share the conifer forests with lodgepole chipmunks?
C、Ecologists have studied the four chipmunk species that occur on the eastern slope of the Sierra and have learned just how these species interact while remaining separate, each occupying its own elevational zone. The sagebrush chipmunk is found at the lowest elevation, among the sagebrush. The yellow pine chipmunk is common in low to mid-elevations and open conifer forests, including pihon and ponderosa and Jeffrey pine forests. The lodgepole chipmunk is found at higher elevations, among the lodgepoles, firs, and high-elevation pines. The alpine chipmunk is higher still, venturing among the talus slopes, alpine meadows, and high-elevation pines and junipers.Obviously, the ranges of each species overlap.Why don’t sagebrush chipmunks move into the pine zones? Yet each species remains within a fairly well-defined elevational zone. Why don’t alpine chipmunks move to lower elevations and share the conifer forests with lodgepole chipmunks?
D、Ecologists have studied the four chipmunk species that occur on the eastern slope of the Sierra and have learned just how these species interact while remaining separate, each occupying its own elevational zone. The sagebrush chipmunk is found at the lowest elevation, among the sagebrush. The yellow pine chipmunk is common in low to mid-elevations and open conifer forests, including pinon and ponderosa and Jeffrey pine forests. The lodgepole chipmunk is found at higher elevations, among the lodgepoles, firs, and high-elevation pines. The alpine chipmunk is higher still, venturing among the talus slopes, alpine meadows, and high-elevation pines and junipers.Obviously, the ranges of each species overlap.Why don’t sagebrush chipmunks move into the pine zones?Why don’t alpine chipmunks move to lower elevations and share the conifer forests with lodgepole chipmunks? Yet each species remains within a fairly well-defined elevational zone.
答案B
解析
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