Convergent evolution is result of analogous structures which develop in organisms as a result of independent development of similar form and feature by unrelated organism as an adaptation to a similar environment. 

• Adaptive radiation is evolutionary process in which different species starting from a common point.
  
• Adaptive radiation generally occurs when an organism enters a new area and different traits affect its survival. 
  
• An example of adaptive radiation is development of mammals after extinction of dinosaurs.
  

Homo habilis had same dental formula of man. They had dental formula 2123/2123. The or options are characters of Homo habilis.

The primitive reducing atmosphere of earth was rich in water vapour, carbon monoxide, carbon dioxide and hydrogen. Absorption of infrared radiation by green house gases ($C{O}_2$ and $C{H}_4$) imparted high temperature to primitive earth. The high temperature, UV light and lightening facilitated reaction between above mentioned elements to form simple organic compounds. Abundant hydrogen combined with free oxygen, nitrogen and carbon to form water, ammonia, methane and cyanides. These early gases got dissolved and wash down with rain water into sea/oceans reby adding organic compounds to sea water. This was followed by formation of saturated and unsaturated hydrocarbons and ir derivatives by combination of highly reactive free radicals (-CH, -CH${}_2$ etc) as facilitated by high temperature of sea water. The hydrocarbons, ir derivatives, ammonia and water exhibited condensation, polymerisation and redox reactions to form simple sugars, amino acids, fatty acids, purines and pyrimidines which in turn served as monomers for formation of more complex polymers. Polymerization was carried out by dehydration synsis i.e., removal of water molecules to join monomers toger and was partly facilitated by high temperature of sea water. This makes option A correct.