The following table shows several bacterial strain lac operon genotypes (Note that some are partial diploids). Fill in the blanks in the “lactose absent” and “lactose present” columns in this table.  (A) means significant levels of active ß-galactosidase enzyme can be detected.  (B) means no significant levels of active ß-galactosidase enzyme are produced. The first line is filled in for reference.    Strain genotype Lactose absent Lactose present  lacI+ lacP+ lacO+ lacZ+ lacY+ B A lacI+ lacP+ lacOc lacZ–  lacY+ [ Select ] B A [ Select ] B A  lacI+ lacP+ lacOc lacZ+lacY- [ Select ] A B [ Select ] B A lacI+ lacP– lacO+ lacZ+ lacY+  [ Select ] B A [ Select ] B A lacI– lacP+ lacO+ lacZ+ lacY+ / lacIs [ Select ] B A [ Select ] A B  lacIs lacP+ lacOc lacZ+ lacY+/ lac I+ [ Select ] A B [ Select ] A B  多重下拉选择题