重點講解：
1. extraterrestrial life 外星生物
例句：Of course, there is always the chance that extraterrestrial life will find us first.
當然，很有可能外星生命先發(fā)現我們。

2.tear up 撕毀
例句：I suggest that you tear up the letter and start over again.
我建議你把這封信撕了，再重頭開始寫。

3.turn it upside down 把它顛倒；完全顛覆
例句：It was stupid of you to turn it upside down without closing the lid.
你沒有蓋上蓋子就把它倒過來，真是糊胡涂。

4.protect..against 保護；幫助抵抗
例句：Container scanning services are offered to help protect against security risks associated with international trade .
集裝箱掃描服務將幫助防止與國際貿易有關的安全風險。