问题
单项选择题
Compared to normal markets, the existence of fraud and the use of violence in black markets generally leads to:（）
A. poorer economic efficiency.
B. superior economic efficiency.
C. lower profit rates for sellers.
答案
参考答案：A
解析：
Fraud and violence lead to a lower level of economic efficiency in black markets. The black markets operate less smoothly. The sellers that are not caught can charge a higher price for the risks they take and earn a higher profit rate.