保险: insurance, to insure, safe, secure, be sure, be bound to...
微观: micro-, subatomic...
造纸术: papermaking technology...
搭乘: to ride as a passenger, to travel by (car, plane etc)...
担忧: to worry, to be concerned...
界线: limits, bounds, dividing line...
汗水: sweat, perspiration...
下坠: (of objects) to fall, to drop, to droop, (medicine) to experience tenesmus...
