Balbiani rings are the sites of RNA synthesis, Lipid synthesis, Nucleotide synthesis, Polysaccharide synthesis

Balbiani rings are a large puff of polytene chromosomes present during larval development in Dipterians. The puffs constitute a gene or group of genes that are actively synthesising RNA. The RNA is transported to the cytoplasm to carry out protein synthesis. Balbiani rings are the site of RNA synthesis only. So, the correct answer is option A.