A metal ore includes the oxide, MO. Metal M produces coloured compounds. If a piece of iron is added to a solution that contains aqueous $\text{M}^{2+}$ ions, M is displaced. Which row is correct?
- Adensity of M: high; possible method of extraction of M from MO: electrolysis only
- Bdensity of M: high; possible method of extraction of M from MO: electrolysis or heating with carbon
- Cdensity of M: high; possible method of extraction of M from MO: heating with carbon only
- Ddensity of M: low; possible method of extraction of M from MO: heating with carbon only