重点讲解：
1. on alert 处于警戒状态；保持戒备；
例句：Security forces were placed on alert.
治安警备力量进入了警戒状态E^WqcbzWN7Jij.Gd。
2. turn over (使)翻转；(使)颠倒；(使)倾覆；
例句：Liz picked up the blue envelope and turned it over curiously.
莉兹拿起蓝色信封，好奇地翻过来看V_^U)%C4mAO~thle。
3. to be honest 老实说；说实在的；
例句：To be honest, I have stopped reading papers for years now.
实话说，我已经好几年不看报纸了Mr624T9M_rMyFe0y.%o#。
4. under threat 受到威胁；
例句：The biologist believes that some animal species are under threat of extinction.
那位生物学家相信某些动物物种正受到灭绝的威胁r6X=&7d8l9TMe。
5. even though 即使；尽管；纵然；
例句：I don't like spinach even though I know it's good for me.
我不喜欢吃菠菜，虽然我知道它对我有好处Q*#j~b^eR1o6.9t#w。