四、符号说明
1.谓语动词用黑体的斜体字表示，例如：Everyone should know …。
2.从句的引导词用方框表示，例如：where the nearest fire alarm box is located。
3.从句用横线表示，例如：where the nearest fire alarm box is located，表示where引导的从句。
4.插入语成分用括号表示，例如：Keeping your head, (instead of crowding and pushing to get to an exit), may make the difference between…
