问题
单项选择题
In a natural monopoly:（）
A. one firm controls all natural resources.
B. the government reserves the industry sector dealing with natural resources for a few firms only.
C. the average total cost of production continually declines with increased output.
答案
参考答案：C
解析：
A monopoly situation in which the average total cost of production continually declines with increased output is called a natural monopoly.