生产安全事故按原因可分为哪几类？

模仿示例，简析下面广告语的丰富内涵。（3分）

示例：

某旅游景点的一则告示：“除了脚印，什么都别留下：除了记忆，什么都别带走。”

答：此告示让游客在逆向思维中揣摩、感悟语言酌精妙，体会出“什么”的言外之意：第一个“什么”指不要攀摘花木、乱涂乱画乱扔果皮纸屑等；第二个“什么”指不要带走景区的任何东西。它提醒游客文明游览，语言表达委婉巧妙，让人易于接受。

《法制文萃报》：好人得好报。

答：                                                                     

Jesse Owens was born in Alabama in the USA, in 1913. There were ten children in his family. Jesse was the youngest. He went to school in the city of Cleveland. At school he showed he had a special talent for athletics (田径). He could run fast. He could jump high. He could jump far. Because he was good at athletics, Jesse became a student at Ohio State University.

　　   In May, 1935 in Michigan, USA, he broke the world record for the long jump. This was his first world record. On the 25th May Jesse did something unusual. In 45 minutes he broke six world records. Some people think that this was the greatest athletics achievement ever.

　　   In 1936 Jesse went to the Olympic Games in Berlin, Germany. There were only nineteen black athletes in the USA team. He won gold medals in the 100 meters race, the 200 meters race, the long jump and the relay race.

　　   Jesse was not a professional athlete. This meant that he could not get money for running. Later, he became a professional athlete. To make money he had to appear in strange races. Sometimes he had to race against horses.

　　   In 1960 somebody broke Jesse's last world record. In 1980 Jesse died.

小题1:Jesse Owens was born in _____in the USA.

A. Alabama    B. Cleveland    C. Ohio    D. Michigan

小题2:Jesse showed he was very good at ______ when he was at school.

A．basketball

B．swimming

C．athletics

D．shooting小题3:Jesse's first world record was for the ______.

A．running

B．relay race

C．high jump

D．long jump小题4:He won ______ gold medals in 1936 in the Olympic Games in Berlin, Germany.

A．two

B．four

C．six

D．eight

就风险而言，从大到小的排列顺序为：公司证券、金融证券、政府证券。

燃料燃烧的基本条件有哪些？

航空障碍灯、摄像头等无金属外壳或保护网罩的外部用电设施应在接闪器保护范围内，其供电配电盘（柜）宜单独安装出冲击电流limp不小于（）kA的SPD。

A、10

B、12.5

C、15

D、17.5