Chromatography is a useful method for purification of elements which are:

The correct option is A available in minute quantities

• Chromatography is based on the principle that different components of a mixture are adsorbed to a different extent on an adsorbent. The mixture is put onto a stationary phase which may be a solid or a liquid.
• A pure solvent, a mixture of solvents or a gas is allowed to move slowly over the stationary phase. Different components of the mixture get separated gradually as the moving phase moves
  
• Chromatography is very useful for purification of the elements which are available in minute quantities and the impurities are not very different in chemical properties from the element to be purified.