In primitive environment of sea, rapid polymer formation was possible because of 

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 thereby adding organic compounds to sea water. This was followed by formation of saturated and unsaturated hydrocarbons and their derivatives by combination of highly reactive free radicals (-CH, -CH${}_2$ etc) as facilitated by high temperature of sea water. The hydrocarbons, their 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 synthesis i.e., removal of water molecules to join monomers together and was partly facilitated by high temperature of sea water. This makes option A correct.