Which of the Following Combinations Will Produce the Highest Expression

Multiple Choice

Which of the following combinations will produce the highest expression of ?-galactosidase? Assume crp^- is a complete deletion of CRP (cAMP receptor protein) .

A) lacI⁺,crp^- on medium with glucose but no lactose
B) lacI^s,crp^- on medium with lactose but no glucose
C) lacI⁺,crp^- on medium with both glucose and lactose
D) lacO^c,crp⁺ on medium with glucose but no lactose
E) lacO^c,crp⁺,on medium with both glucose and lactose