An E. coli strain is lac Z. The structural gene for ß-galactosidase is encoded at the lac Z locus. How would you describe the regulation of lactose metabolism in these cells?

A.	normal regulation of lactose metabolism.
B.	constitutive expression of lac Z+.
C.	inability to synthesize the lac Z+ gene product, ß-galactosidase.
D.	lac Z+ gene is inducible, but unable to be repressed by high glucose.
E.	no synthesis of the lac I gene product, the lac repressor.