Which of the Following Statements About Constitutive Genes Is False

Which of the following statements about constitutive genes is false?

A) Constitutive genes produce their proteins when a cell encounters a specific environmental change.
B) Constitutive genes are expressed at any given time.
C) Constitutive genes function differently than facultative genes.
D) Constitutive genes are referred to as housekeeping genes.
E) Constitutive genes account for less than 20 percent of a cell's genes.