Calibration curve In the calibration curve below the absorbance for the 2.0 mg/L standard appears to be too high. Which of the answer below is not a source of possible error? Calibration curve for detemination of Fe 2+ concentration 0.900 0.800 0.700 0.600 0.500 Absorbance at 510 nm 0.400 0.300 0.200 0.100 0.000 + 0.00 1.00 2.00 3.00 4.00 5.00 Fe2+ (mg/L) O a Light scattered by dirt on the cell O b. Flask or equipment contaminated Oc. Volumetric flask not diluted to the mark O d. Attention to detail of procedures