题目

 With the pressure of being off work ______, Mary seemed to be going crazy.   A. making up        B. taking up C. picking up        D. building up   答案：D 12．铁丝在氧气中燃烧的实验现象为剧烈燃烧、火星四射、生成了黑色固体物质，放出了大量的热，化学符号表达式表达式为3Fe+2O2$\frac{\underline{\;点燃\;}}{\;}$Fe3O4，集气瓶中加入液体的作用是防止溅落的熔化物炸裂瓶底．