用KMnO滴定Fe+，达sp点时，有关离子浓度关系正确的是A[Fe+]=[Mn+]，[Fe+]=[MnO–]B[Fe+]=[Mn+]，[Fe+]=[MnO–]C[Fe+]=[Fe+]，[Mn+]=[MnO–]D[Fe+]=[Mn+]，[Fe+]=[MnO–]