Other Than the Proteins That They Encode, What Is a Major

Other than the proteins that they encode, what is a major difference between cell-specific and housekeeping genes? ​

A) Cell-specific genes are expressed only in a single cell type; housekeeping genes are expressed in all cell types.
B) Cell-specific genes have promoter proximal elements and enhancers; housekeeping genes have only promoter proximal elements.
C) Cell-specific genes have promoter proximal elements that use cell-specific activators; housekeeping genes use "universal" activators.
D) Cell-specific genes are only found in certain cell types; housekeeping genes are found in all cell types.
E) Cell-specific genes have promoter proximal elements that use "universal" activators; housekeeping genes have promoter proximal elements that respond only to specific activators.