VOA慢速英语:你可能会对美国最危险的地方感到惊讶

calculate- v. to get a general idea about the value of something

tornado- n. a violent and destructive storm in which powerful winds move around a central point

county- n. an area of a state or country that is larger than a city and has its own government to deal with local matters

hazard- n. a source of danger

vulnerability- n. the state of being open to attack, harm or damage

infrequent- adj. an act that does not happen often