Article 20:An offer becomes void if: 第二十条有下列情形之一的，要约失效： (1)a rejection of the offer reaches the offeror; (一)拒绝要约的通知到达要约人； (2)the offeror lawfully revokes the offer: (二)要约人依法撤销要约： (3)the fixed time for acceptance expires without acceptance by the offeree;or (三)承诺期限届满，受要约人未作出承诺； (4)the offeree materially alters the particulars of the offer. (四)受要约人对要约的内容作出实质性变更。 Article 21:An acceptance is the offeree's declaration of his intent to assent to an offer 第二十一条承诺是受要约人同意要约的意思表示。 Article 22:An acceptance shall be manifested by means of notification,unless usage of trade permits that acceptance be manifested by performing an act or the offer indicates that acceptance may be manifested by performing an act. 第二十二条承诺应当以通知的方式作出，但根据交易习惯或者要约表明可以通过行为作出 承诺的除外。 Article 23:An acceptance shall reach the offeror within the time fixed in the offer. 第二十三条承诺应当在要约确定的期限内到达要约人· If no time for acceptance is fixed in the offer,the acceptance shall reach the offeror by the time specified below: 要约没有确定承诺期限的，承诺应当依照下列规定到达： (1)if the offer is made to a person who is present,the acceptance shall be made promptly,unless otherwise agreed by the parties; 66 Article 20: An offer becomes void if: 第二十条有下列情形之一的，要约失效： (1) a rejection of the offer reaches the offeror; （一）拒绝要约的通知到达要约人； (2) the offeror lawfully revokes the offer; （二）要约人依法撤销要约； (3) the fixed time for acceptance expires without acceptance by the offeree; or （三）承诺期限届满，受要约人未作出承诺； (4) the offeree materially alters the particulars of the offer. （四）受要约人对要约的内容作出实质性变更。 Article 21: An acceptance is the offeree’s declaration of his intent to assent to an offer. 第二十一条承诺是受要约人同意要约的意思表示。 Article 22: An acceptance shall be manifested by means of notification, unless usage of trade permits that acceptance be manifested by performing an act or the offer indicates that acceptance may be manifested by performing an act. 第二十二条承诺应当以通知的方式作出，但根据交易习惯或者要约表明可以通过行为作出 承诺的除外。 Article 23: An acceptance shall reach the offeror within the time fixed in the offer. 第二十三条承诺应当在要约确定的期限内到达要约人。 If no time for acceptance is fixed in the offer, the acceptance shall reach the offeror by the time specified below: 要约没有确定承诺期限的，承诺应当依照下列规定到达： (1) if the offer is made to a person who is present, the acceptance shall be made promptly, unless otherwise agreed by the parties;