Suppose an operon has the following characteristics: (1) The operon codes for structural proteins that convert compound Q to compound B. (2) The operon is controlled by a constitutively expressed regulatory gene called reg. (3) In wild-type individuals, the operon is transcribed in the absence of compound B but not in the presence of compound B. (4) In reg- mutants, the operon is constitutively transcribed. Is this operon inducible or repressible? Why?