From the following, the ores that are concentrated by froth flotation are:

a. Haematite b. Galena
c. Copper pyrites    d. Magnetite

Choose the correct option:
1. a and b
2. b and c
3. c and d
4. a and d

HINT: Sulphide ores are extracted by froth floatation method.
The basic principle applied in the process of Froth Flotation is the difference in the wetting ability of the ore and remaining impurities.
Haematite Fe2O3 and magnetite Fe3O4 are oxide ores while galena PbS and copper pyrites Cu FeS2 are sulphide ores. As we know sulphide ores are extracted by using froth floatation method.
Hence, (b) and (c) are the correct choices.