关于承诺的正确表述为( )。

A．受要约人超过承诺期限发出承诺的，除要约人及时通知受要约人该承诺有效的以外，为新要约

B．受要约人超过承诺期限发出承诺的，除要约人及时通知受要约人该承诺失效的以外，为有效

C．承诺可以撤销，撤销承诺的通知应当在承诺通知到达要约人之前或者与承诺通知同时到达要约人

D．承诺不得撤回，但可以撤销

In each person’s life there are three stages. When one was young, people said, "He will do something." As he grew older and did nothing, they said, "He could do something if he found himself." When he was white-haired, people said of him, "He might do something if he could try anything."

A．He should have done something if he has tried something

B．He would have done something if he should have tried anything

C．He might do something if he would try something.

D．He might have done something if he had tried anything