要约失效的情形有哪些?
参考答案:
要约失效的情形:拒绝要约的通知到达要约人;要约人依法撤销要约;承诺期限届满,受要约人未作出承诺;受要约人对要约的内容作出实质性变更。
生态系统的最终能量来源于[ ]
A.绿色植物
B.吃植物的动物
C.空气和土壤
D.阳光
Which of the following most accurately describes a market structure that has one seller of a specific, well-defined product that has no good substitutes()
A. Oligopoly.
B. Monopoly.
C. Monopolistic competition.