Hxen.com's tips：Every day persisted can learn English well!-->■Learn English Everyday■
flip – v. to change from one state, position, subject, etc., to another
hunker down – phrasal verb to lower the body to the ground by bending the legs : to stay in a place for a period of time to remain safe
degree – n. a step or stage in a process, course, or order of classification
column – n. something that is tall and thin in shape
