Hxen.com's tips：Every day persisted can learn English well!-->■Learn English Everyday■
mask – n. a covering for the face, especially used to cover the nose and mouth to prevent the spread of disease
density – adj. the amount of something in a defined area
bill –n. paper money
county –n. an area of a state or country this is larger than a city and has its own local government
miracle – n. a wonderful event
quarantine – n. a situation of being kept away from others to prevent the spread of disease
symptom – n. a sign or effect that shows disease is present
jungle – n. a thick forest in areas near the Equator of the Earth
