There are four distinct types of rRNA in 80s ribosomes which include 28s rRNA, 5s rRNA, 18S rRNA and 5.8S rRNA. RNA polymerase I is involved in the synthesis of 18S, 5.8S and 28S rRNA. RNA polymerase II is involved in synthesizing mRNA. RNA polymerase III is responsible for the synthesis of 5S rRNA and tRNA. So, there are two types of RNA polymerase (RNA polymerase I and III) that are involved specifically in the synthesis of all rRNA of 80s ribosomes.