Pledge绝对不是发誓，只能是宣誓，如向某某团结或国家表示效忠。Promise也不对，promise是承诺的意思。答案惟有swear, make a swear, make a swearing promise，swear/make one's oath, vow，take a vowlianggc的答案涵盖较正确。
发誓: 1. to vow2. to pledge3. to swearRelative explainations: Examples:1. 他发誓要戒烟。 He swore to abstain from smoking.2. 骑士发誓要为他父亲向敌人报仇。 The knight swore he would revenge his father's death.3. 他发誓永远爱她。 He swore to love her for evermore.4. 他们发誓要忠实履行自己的职责。 They swore an oath to carry out their duties faithfully.5. 他已经发誓对这件事保密。 He has been sworn to secrecy about this.6. 战士们发誓战斗到底。 The soldiers swore to fight it out.7. 我对万能的上帝发誓我要说真话。 I swear by Almighty God that I will tell the truth.8. 他们发誓要向绑架者报仇. They swore to take their revenge on the kidnappers. To utter curses; swear.诅咒；发誓To make a vow; promise.发誓；许诺Take the vows of a nun.发誓成为一个尼姑To renounce or repudiate under oath.放弃，发誓抛弃He took an oath to give up smoking.他发誓戒烟。To renounce under oath; forswear.发誓放弃；发誓革除I've sworn off smoking.我已发誓戒烟。He vowed obedience.他发誓要服从。To disavow under oath; deny.发誓否认；坚决否认Abjure one's beliefs.发誓放弃某人的信仰
