重点讲解：
1. thanks to 幸亏；归因于；
Thanks to the automobile, Americans soon had a freedom of movement previously unknown.
由于有了汽车，美国人很快就获得了前所未有的行动自由。
2. have a handle on （理解、解决问题的）方法，途径；
This one was a doozy but we think we finally have a good handle on it now.
这个问题有点麻烦，不过我们认为现在已经能很好的处理它了。
3. react to （作出）反应；回应；
Someone allergic to milk is likely to react to cheese.
对牛奶过敏的人可能对奶酪也有不良反应。
4. rely on 依赖；依靠；
Many animals rely on concealment for protection.
许多动物靠藏匿自己来避害
