An ore of tin containing ${\mathrm{FeCr}}_2{\mathrm{O}}_4$is concentrated by:

An ore of tin containing ${\mathrm{FeCr}}_2{\mathrm{O}}_4$ is concentrated by magnetic separation.

Magnetic separation is based on variations in the magnetic characteristics of the ore constituents.

This type of separation is used when either the ore or the gangue is drawn toward the magnetic field.

For instance, since a magnet attracts iron ores, non-magnetic impurities may be extracted from them via magnetic separation.

Here, magnetic separation can separate ${\mathrm{FeCrO}}_4$ since it is iron ore.

Hence, option A is correct.