Identifying M by extraction, reactivity, and compound color

Steps:

• Extraction from oxide by carbon reduction or electrolysis identifies moderately reactive metals like iron (carbon in blast furnace) and magnesium (electrolysis of MgCl₂).
• Reaction with dilute HCl excludes less reactive metals like copper, which does not react appreciably.
• Formation of colored compounds fits iron (e.g., Fe²⁺ green solutions) but not typically magnesium (colorless ions); however, options allow selection of fitting pair.
• Comparing choices, only iron or magnesium satisfies all criteria without contradiction.

Why D is correct:

• Iron and magnesium align with reactivity series positions for carbon/electrolysis extraction and HCl reaction, per standard reduction methods (e.g., Fe₂O₃ + 3C → 2Fe + 3CO).

Why the others are wrong:

• A: Copper does not react with dilute HCl.
• B: Same as A; copper fails acid test.
• C: Excludes magnesium, which fits electrolysis extraction.

Final answer: D