Hematoxylin becomes a dye only after oxidation. Which option best completes this statement?

• A. It Is Oxidized
• B. It Is Reduced
• C. It Is Absorbed
• D. It Is Crystallized

Answer: (A)

Hematoxylin must be turned into its active form to function as a dye. When hematoxylin is oxidized, it becomes hematein, which then forms a colored complex with a metal mordant (such as aluminum or iron). This complex is what actually binds to tissue components, especially nuclei, producing the characteristic stain. Reduction would not activate the dye, absorption describes uptake rather than activation, and crystallization is not part of the staining mechanism. So, the statement is completed by: It Is Oxidized.