A:Does an acceptance once given cannot be revoked?

　　承诺一经作出即不得撤回吗？

　　B:An acceptance once given cannot be revoked the offeror consents.

　　除非要约人同意，承诺一经作出即不得撤回。

　　The teaching quality will not be changed unless change teaching facilities.

　　除非改善教学设施，教学质量不会改变。

　　He can not accept the requirment unless you apologize him.

　　除非你向他道歉，他不会接受这要求。

　　He can not offer the change unless you have the ability.

　　除非你有能力，他不好给你机会。

　　延伸阅读:

　　A:What's the issue of the action?

　　这案件的争议是什么？

　　B:The issue of this action is the date of the contract.

　　这案件的争议是合约的日期。

　　The issue of this action is the content of the contract.

　　这案件的争议是合约的内容。

　　The issue of this action is the form of the contract.

　　这案件的争议是合约的形式。

　　The issue of this question is the date of the application form.

　　这问题的争议是申请表的日期。