72. Which of the following statements about lac operon is CORRECT? ① The repressor is theprotein product of lac Z gene. ② The lac operon can be turned on by β-galactoside. ③Repressor binds to the operator and blocks the binding of RNA polymerase to promoter. ④Isopropyl-β-D-thiogalactoside can bind to Lac repressor to turn on protein expression. ⑤ In thelac operon model, the genes within the operon will be expressed if lactose is present in E. coli.
(A) ①,②,③
(B) ①,②,④
(C) ②,③,④
(D) ③,④,⑤
(E) ②,③,④,⑤