阅读下文，回答问题

祸从天降，谁为真凶

陈祺

      ①2010年8月7日，一场突如其来的灾难降临甘肃省舟曲县，昔日秀美的山中小城顿时满目疮痍,许多同胞不幸罹难。罪魁祸首,就是泥石流。那么，泥石流到底是怎么发生的呢?

      ②泥石流是暴雨、洪水将含有沙石且松软的土质山体经饱和稀释后形成的洪流。相对于普通洪水，泥石流含有大量泥沙石块等固体碎屑物，最高体积含量可达80%，因而具有更大的破坏力。它往往发生在山区等沟谷深壑、地形险峻的地区。

      ③舟曲县城所在的白龙江地区地势起伏较大，山谷地势高差达1000-2000米，而且舟曲正好处于两山之间的峡谷地带，这给泥石流汇集和流动形成了天然的地理条件。舟曲位于龙门山地震活动带北缘，又临近天水地震活动带。由于历史上的几次大地震，舟曲附近的地质构造岩性松软、破碎，风化程度严重，堆积物很多。此外，灾害发生之前持续的干旱造成附近山体干缩，加大了岩石间、山体间的缝隙，使原本已十分松散的岩体、山体互相之间更加没有黏性。

      ④这些地质条件给舟曲埋下了安全隐患，但如果没有力量去推动这些松散物质的话，泥石流依然不会发生。暴雨就是推动泥石流的“手”。

      ⑤处于黄土高坡上的舟曲县原本是一个干旱的地区，多年的平均年降水量不到200毫米。有历史记载的暴雨近百年来只发生过2次，分别是1973年7月 12日的57．2毫米暴雨和1994年8月8日的63．3毫米暴雨。本次舟曲泥石流暴发当晚，该地区在短短40分钟内突降97毫米的大暴雨。大量的水浸透沟床中的固体堆积物质，使其稳定性降低。饱含水分的固体堆积物在自身重力作用下发生运动，形成了泥石流。作为生命之源的水成了这场灾难的导火索和帮凶。

      ⑥如果说强降雨是“导火索”的话，山体风化、水土流失则是“火药”，而人类活动担当了“催化剂”的角色。

      ⑦20世纪50年代，舟曲县森林覆盖面大，生态环境平衡，有“陇上江南”之称。然而之后的半个多世纪，舟曲的森林覆盖率从67%锐减到20%。森林的过度砍伐导致舟曲水土流失严重，山体风化，土地裸露，一旦遇到狂风暴雨，泥石流就容易形成并沿着山谷倾泻而下。另外，近10年来，舟曲县获批的大小水电站有55座。修建水电站要炸山辟地，会令岩体变得松动，植被遭到破坏，制造了大量的松散物质。更有甚者，舟曲矿产资源丰富，开矿遗留的废弃土石处理不当，使松散碎屑物质量大增。这样，在自然状态下需数十、数百乃至上千年才能聚集起来的松散碎屑物质量，现在几年内便达到了。桶里装满了“火药”，自然一点就炸。

      ⑧由此可见，舟曲泥石流的形成不完全是因为天灾，人为因素也促进了泥石流的发生发展，扩大了它的规模，加重了危害程度。在经济发展中应该重视环保，只有真正贯彻落实可持续发展，才能避免悲剧重演。

(选自《中学科技》2010年10期，有改动)

下图是2011-2014年我过货物出口额和进口额情况。由图可知，近年来我国(    )

Authors (作者)

    Alexandru Micu: Author

    ZME Science author profile | e-mail: alex@zmescience.com

    Main focus: technology, biology

    Curiosity (好奇心) is what drives Alex forward-his interest in learning more about the planet being matched only by his ability to discuss things with a light heart. Alex tries to make others more interested in special science and technology. He does things in his own way.

    Dragos Mitrica: Author

    ZME Science author profile | e-mail: dragos@zmescience.com

    Main focus: wheather

    Dragos loves nature, and does everything he can to understand it. This interest led him to many unexpected places in his life, and now, he mainly studies and understands how ancient (古代的) weather changed, and what this means for the future.

    Henry Conrad: Author

    ZME Science author profile | e-mail: henrykconrad@gmail.com

    Main focus: technology

    Henry Conrad is a game developer from Albuquerque, New Mexico. Whenever he's not working or reading the latest tech news, he enjoys writing about the latest inventions and technology, which benefits (有益) him a lot. It helps him find rich writing materials (材料).

    Mihai Andrei: Editor-in-chief

    ZME Science author profile | e-mail: andrei@zmescience.com

    Main focus: geophysics, environment

    Andrei has put a lot of sweat and tears into ZME Science ever since he was a student. He is always looking for the most interesting subjects, presenting them in a way that everybody can understand. He believes that education is the key towards a better future and he tries to persuade people to become better persons of the planet. His background is in Geology and Geophysics, but now, he focuses more on environmental studies.

    It is Monday morning. Mary, Lucy, Tina and Judy____in the classroom.

    Mary says she loves____because she loves Christmas(圣诞节). She can have a____time with her family. And she doesn't like June.

    Lucy likes July____she likes the summer holiday(暑假). In July, her parents take____to travel(旅行). It's really great.

    Tina thinks the ____month is good. People can go out with____ and families. They can have a great ____together（一起）.

    Judy likes October because her birthday is on the tenth day in this ____. She usually has a good time on her____.