质量分数为30%的某溶液蒸发掉10g水后,溶质的质量分数变为40%,则原溶液的质量是请选择DCBA5L;w9E1V+U+y;n(_
A.30g+y;n(_
B.40g+y;n(_
C.50g+y;n(_
D.60g+y;n(_