Answer:
C. A mutation in the operator sequence
Explanation:
The operator sequence of the lac operon serves as the site for the binding of repressor protein. When repressor protein is bound to the operator sequence, the enzyme RNA polymerase is inhibited to carry out the process of transcription of the structural genes of the operon. Binding of allolactose to repressor does not allow it to bind to the operator sequence. This allows the expression of the lac operon in the presence of lactose sugar.
Any mutation in the operator region that disturbs the binding of the repressor to it would allow the expression of lac operon even in the absence of lactose allowing it to be expressed in a constitutive manner.
The best answer is "Chemistry, biology, and engineering"
Taking courses in chemistry, biology, and engineering would best prepare someone for a career in biotechnology, due to the intersection of of technology and biology, and the need for chemistry to better understand biological systems.