Answer:
D) presence of transcription activators or repressors
Step-by-step explanation:
The reason why this is not post-transcriptional regulation is that activators actually start the process of transcription by binding to specific sites. while on contrary when repressor binds it halt the process.
For example, there is a protein called CAP which in the presence of cAMP bind with promoter region and enhances the activity of RNA polymerase . While in the absence of cAMP it can not bind to promoter hence the transcription stooped.