OG4 阅读 Q18

Choice A is the best answer. In lines 66-68("Virtually... conducted"), the author notes that American cities in 1974 each had a "downtown, where the commercial life of the metropolis was conducted." In this context, the author is stating that these cities "conducted," or carried out, business, the "commercial life," in down-town areas.
Choices B, C, and D are incorrect because in this context, "conducted" does not mean supervised, regulated, or inhibited.