22.滴定30.0mL某Sn2+酸性溶液，達滴定終點時共消粍了 10.0 mL KMn04溶液(0.120 M) ＞此溶液中Sn2+之起始濃度為何？
(A)0.100
(B)0.200
(C)0.360
(D)0.900
(E)0.600