当需要特征提取分析时，最好例子是什么？
What is the best example of when feature extraction analysis would be needed?
A、识别海洋石油泄漏的程度
To identify the extent of an oil spill in the ocean
B、识别一个县的土地覆盖类型
To identify land cover types in a county 
C、识别一个县内所有铁路的位置
To identify the locations of all railroads in a county
D、识别一个州内所有猫头鹰筑巢地的位置
To identify the locations of all owl nesting grounds in a state