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交换积分次序 $\int_{-1}^0 d y \int_{1-y}^2 f(x, y) d x=(\quad)$
A. $\int_1^2 d x \int_0^{1-x} f(x, y) d y$     B. $\int_1^2 d x \int_{1-x}^0 f(x, y) d y$     C. $\int_0^2 d x \int_0^{1-x} f(x, y) d y$     D. $\int_0^2 d y \int_{1-x}^0 f(x, y) d x$         
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