VOA慢速英语:IS Claims Responsibility for Suicide Bombing at Saudi Mosque

vow – v. to make a serious promise to do something or to behave in a certain way
tyrant – n. a ruler who has complete power over a country and who is cruel and unfair
frustration – n. a feeling of anger or annoyance caused by being unable to do something: the state of being frustrated
presumption – n. a belief that something is true even though it has not been proved