A Key Feature of Regulatory Systems Involving Deletion of a Gene

A key feature of regulatory systems involving deletion of a gene is:

A) the DNA deletion event must be passed to progeny cells
B) the cell can modulate the level of expression of this gene (one cell can express the gene at different levels) in response to different growth conditions
C) the deletion event can occur in any cell type at any time
D) the DNA deletion event must not be passed to progeny or germ?line cells
E) the sigma factor of RNA polymerase is altered