Here's why:

* RNA polymerase is responsible for reading the DNA sequence of a gene and synthesizing a complementary RNA molecule (mRNA). This mRNA molecule then carries the genetic code to the ribosomes for protein synthesis.

* Transcription is the process of copying genetic information from DNA to RNA.

* RNA polymerase acts as a catalyst, facilitating the formation of the phosphodiester bonds that link the nucleotides together in the RNA molecule.

There are different types of RNA polymerase in different organisms, but they all perform the essential function of transcribing DNA into RNA.