在人类社会发展至今存在的基本经济形态中，为了满足生产者自身需要而进行生产的经济形态是
题型：单项选择题
问题：
在人类社会发展至今存在的基本经济形态中，为了满足生产者自身需要而进行生产的经济形态是()。
A.市场经济
B.计划经济
C.商品经济
D.自然经济
题型：单项选择题
A number of bricks were purchased to build a fireplace, at a cost of 40 cents each, but only
of them were needed. If the unused 190 bricks were returned and their cost refunded, what was the cost of the bricks used to make the fireplace ？（）
A.$76
B.$228
C.$304
D.$414
E.$570