Thalassemia and sickle-cell anemia are caused by problems in the synthesis of globin molecules. Select the correct statement.

• A
  Both are caused by a defect in the qualitative synthesis of the globin chain.
• B
  Both are caused by a defect in the quantitative synthesis of the globin chain.
• C
  Thalassemia is caused by the reduced synthesis of globin molecules.
• D
  Sickle-cell anemia is caused by a quantitative problem of the globin molecule.