【正确答案】 A

【答案解析】依据文章第三段第一行、第二行：As the intelligence of robots increase to match that of humans and as their cost declines through economies of scale we may use them to expand our frontiers．．．可以看出机器人被用来拓展领域的前提有两个：智能的提高和成本的降低。A项符合题意。