Answer:
Negative inducible.
Explanation:
Operon may be defined as the cluster pf genes that are expressed by the single RNA polymerase. The operon includes in the example of the the polycistronic genes.
Negative inducible operon includes the binding of regulatory protein with the DNA and inhibits transcription. The regulatory protein binds with the operator that prevents RNA polymerase transcription. The mutation in the negative inducible operon prevents the binding of repressor to the small molecule.
Thus, the correct answer is option (a).