单项选择题
According to the passage, a barter economy can lead to （）
A. rapid speed of transaction B. misunderstanding C. inflation D. difficulties for the traders
单项选择题 According to the passage, who has the greatest degree of control in an administered system（）
单项选择题 The panel is made up of （）
单项选择题 How will the government know what the air quality is（）
