求问三道微观经济学英文选择题的解析

1、which one of the following is a factor of production?
A. the profits made by firms
B. land owned or rented by firms
C. money held by firms in bank accounts
D. the productivity of labour
答案是B，但为什么不能是其他选项呢？

2.the price of cocoa more than doubled over an 18-month period as a result of increased buying on world markets. such a development in the cocoa market could be shown on a supply and demand diagram by
A.a movement along the demand curve to the left
B.a movement along the demand curve to the right
C.a shift of the demand curve to the right
D.a shift of the demand curve to the left
答案是C，有两个疑问：第一，商品价格上涨，需求曲线不该是向左移动吗？为什么是右？
第二，B和C选项表述上有什么不同？

3.the role of prices in a market economy is to
A. allocate scarce resources
B. provide a mechanism for firms to make profits
C. improve the distribution of income
D. determine the elasticity of demand curves
答案是A，不是很明白问题和答案的意思

1.
factors of production:
land,capital,work,technology

2.
the differences between a shift along the curve and a shift of the curve

3.
市场经济中价格的作用是什么（扮演什么角色）？
A.分配稀缺资源
B.提供一种机制使得厂商获得利润
C.改善收入分配
D.决定需求曲线的弹性