Final answer:
The correct order from left to right for the components involved in transcription is promoter, operator, and then structural genes, since that is the sequence in which the RNA polymerase encounters them during the process of transcription.
Step-by-step explanation:
To answer the question about the proper order of terms assuming transcription occurs from left to right, we need to consider the structure of an operon, which is a unit of DNA containing a cluster of genes under the control of a single promoter. Specifically in prokaryotes, such as bacteria, an operon consists of several components in the following order: a promoter, an operator, and the structural genes. The promoter is where RNA polymerase binds to initiate transcription, the operator is a segment of DNA to which a repressor protein can bind and block transcription, and the structural genes are the actual genes coding for proteins.
Therefore, the correct answer is the one that places these elements in the order in which RNA polymerase encounters them during transcription: c. Promoter, operator, structural genes.