This was a fairly popular question. Many of the candidates who answered the question were able to specify the characteristics of limestone regions but could not describe the formation of limestone pillar. The formation of limestone pillar involves:
-   formed in limestone regions
-   formed within a cave
-   rain water combines with atmospheric carbon dioxide (CO2) to form weak carbonic acid
-   acidic water dissolves limestone
-   dissolution causes calcium bicarbonate
-   the dissolution process wears out materials along limestone joints
-   joints widen and deepen to make rivers drain underground
-   intensification of rock dissolution leads to the formation of underground caves
-   water drips into caves from roof of caves
-   water evaporates leaving behind calcium carbonate residue
-   calcium carbonate residues hang from roofs of caves as stalactites
-   some calcium carbonate residues grow upwards from the floors of caves as stalagmites
-   continuous growth of stalactites and stalagmites join together to form new feature called limestone pillars

The ways in which limestone are important to man were well outlined by majority of the candidates who answered the question.