重點講解：
1. specialise in
專門從事；專門經(jīng)營；專門研究；專攻；
eg. Most of the staff specialise in the care of children.
多數(shù)員工都掌握專業(yè)的兒童保育知識。
eg. As you know, we specialise in electronic games.
正如你們多了解的，我們專門經(jīng)營電子游戲。
2. track down
追蹤到；追查到；搜尋到；
eg. It took the police several days to track down their quarry.
警方用了幾天時間追查到案中目標。
eg. He was determined to track down the cause of food spoilage.
他決心查出食品腐爛的原因。
3. upside down
倒置地；顛倒過來；
eg. The painting is upside down.
圖畫顛倒了。
eg. Tony had an upside-down map of Britain on his wall.
托尼的墻上倒掛了一張英國地圖。