由直线y=12,y=2y = \dfrac{1}{2},y = 2y=21,y=2,曲线y=1xy = \dfrac{1}{x}y=x1及yyy轴所围成的封闭图形的面积是( ).
(A)2ln22\ln 22ln2
(B)2ln2−12\ln 2 - 12ln2−1
(C)12ln2\dfrac{1}{2}\ln 221ln2
(D)54\dfrac{5}{4}45
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