I. Getting started

Why do you think we are exploring Mars or the moon?

II. Vocabulary in use

crash  v. 猛撞，撞毁

用法：crash into a tree 撞到树上；crash into a car 撞车。作动词，还可以指“坠毁，坠落”。作名词时，可指“事故”，a car crash 车祸。