OG4 阅读 Q30

Choice D is the best answer. In lines 63-64("with a... normally active"), the parenthetical is added after the phrase "a promoter," which is "(...a sequence of DNA that controls gene activity)." The parenthetical's purpose is to define the term "promoter."
Choices A, B, and C are incorrect because they do not correctly identify the purpose of the parenthetical information in lines 63-64("with a... normally active").