题目内容
（请给出正确答案）
[多选题]
根据《合同法》，要约失效的情形有()。
A.受要约人拒绝要约的通知到达要约人
B.受要约人的承诺对要约内容做了实质性变更
C.受要约人承诺到达要约人后，要约人发出撤销要约的通知
D.要约中规定的承诺期限届满，要约人未收到承诺通知
E.发出承诺通知前，撤销要约的通知到达受要约人
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M: No, I'm not. But as a psychology major I can use this to fulfill the requirement in developmental psychology.
Q: What do you learn from the conversation？
(14)
A．The two speakers are classmates.
B．The man is majoring in elementary education.
C．The woman is majoring in elementary education.
D．The two speakers got to know each other in a class.
