将质量分数为a％的某物质的水溶液加热蒸发掉m g水（溶质不挥发，且蒸发过程中无溶质析出），所得溶液体积为V L，溶质的质量分数为蒸发前的2倍．设溶质的式量为M，则蒸发后所得溶液的物质的量浓度为（ ）
A． |
B． |
C． |
D． |
相关试题
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