The correct option is A defence action
Secondary metabolism produces a large number of specialized compounds called secondary plant metabolites that do not aid in the growth and development of plants but are required for the plant to survive in its environment. Secondary plant metabolites are several chemical compounds produced by the plant cell through metabolic pathways obtained from the primary metabolic pathways. Many secondary metabolites such as nicotine, strychnine, caffeine, etc are toxic or act as repellants to herbivores and microbes and help defend plants producing them.
Sugars, amino acids, tricarboxylic acids, or Kreb's cycle intermediates, proteins, nucleic acids and polysaccharides are small molecules called primary metabolites. These metabolites are important for growth, nutrition of the organism.