Explanation: The question asks about the significance of cities for pre-modern civilizations. Cities historically have been centers of commerce and religion, among other things, and often were the source of great wealth for states. Eliminate choices that do not reflect this focus. Choice (A) discusses manpower for armies—in pre-modern states most armies were furnished from the countryside and the peasantry, not the urban populations, so eliminate (A). Choice (B) discusses further stratification of society which does not make sense given that cities were the source of mercantile wealth and that wealth often allowed merchants to transcend social barriers, not reinforce them. Eliminate (B). Choice (C) discusses the very merchant activity that cities are historically known for, so keep (C). Choice (D) does feature a known function of cities—religious centers. But this choice uses the word exclusively, and that extreme language precludes any other function of cities, which is not correct. Eiminate (D) and choose (C).