Final answer:
An operon is considered 'Repressed' when a repressor protein binds to its operator site, inhibiting gene transcription. In contrast, 'Constitutive' operons are expressed continuously at steady levels without being affected by the presence of repressors or inducers.
Step-by-step explanation:
When a repressor protein binds to the operator site of an operon in the presence of a specific molecule, it often serves to impede the transcription process.
This mechanism is designed to control the expression of genes within that operon. If the presence of a protein leads to the repressor binding to the operator, resulting in inhibition of gene transcription, then the operon is said to be B) Repressed.
Conversely, an operon that is continuously expressed at constant levels to provide the cell with steady amounts of its protein products, without regulation by repressors or inducers, is called a C) constitutive operon.
In contrast to the inducible or repressible regulation, constitutive expression occurs regardless of environmental conditions or the presence of specific metabolites.