Answer:b.are required for the expression of specific protein-encoding genes
Step-by-step explanation:
Transcription factors are proteins that bind to enzyme RNA polymerase to aid transcription( coping of information on DNA to an intermediate mRNA.
They control the expression of a particular gene. A transcriptor can be a repressor or enhancer. A repressor when they inhibit the action of RNA polymerase by blocking it from attaching to promoter sequence or enhancer by binding to RNA polymerase to enhance transcription.
Transcriptor protein can work alone or work with other protein such as silencer.