求助一道中级微观经济学的题目

If there are only two goods,an increase in the price of good1 will increase the demand for good2:
(A)if and only if price elasticity of demand for good2 is greater than 1 in absolute value
(B)whenever both goods are normal goods
(C)only if the two goods are perfect substitutes
(D)never
(E)none of the above
答案是A,但是我不知道这怎么判断出来的,求大家指点啊!!

第1个回答  2009-11-08
我觉得选C

替代品
第2个回答  2015-10-30
6年了,这还是一道THU中微学界的未解之谜…………
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