Here's why:

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

* mRNA is the type of RNA that carries the genetic code from DNA to the ribosomes, where protein synthesis takes place.

Other types of RNA are produced during transcription, but they are not the primary product:

* tRNA (transfer RNA): Carries amino acids to the ribosomes.

* rRNA (ribosomal RNA): Forms part of the structure of ribosomes.

Therefore, mRNA is the most accurate answer to what best describes the product of transcription.