问题
单项选择题
Natural monopolies exist because they can produce at lower costs with greater output, which means there are economies of scale. Which of the following industries is typically a natural monopoly（）
A. Technology.
B. Utilities.
C. Oil.
答案
参考答案：B
解析：
With a natural monopoly average costs of production will be lowest when a single large firm produces the entire output demanded such as a utility.