单项选择题
A.4B.3C.2D.1
A.E/(1-μ*μ)B.E/(1+μ*μ)C.E/(1-μ)D.E/(1+μ)
A.μ/(1+μ)B.μ/(1-μ)C.1/(1+μ)D.1/(1-μ)
A.1B.2C.3D.4
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