"Undertaking" 是一种常用的表达，表示保证完成任务的意思。这个词源自中古英语 "undertaken", 它的意思是"承担，接受"。
例句:
I give you my undertaking that the work will be completed on time.
(我保证会按时完成这项工作。)
The company gave an undertaking to reduce its carbon emissions.
(公司承诺减少其碳排放。)
She gave an undertaking to the court that she would not contact the victim.
(她向法庭承诺不会联系受害者。)
也可以用 "promise" 表示保证完成任务的意思，这个词源自拉丁语 "promissus"，意思是 "许诺"。
例句:
I promise to finish the project by next week.
(我保证下周完成项目。)
They made a promise to donate a portion of their profits to charity.
(他们答应捐出部分利润给慈善机构。)
He gave his word that he would keep the secret.
(他保证保守秘密。)