第二次工业革命比第一次工业革命更快地推动了生产力的发展的根本原因是（    ）

    2014 is the year of horse in China. Do you know anything about the horse?

    The horse is strong and runs very fast. He's a useful and hard-working animal. The horse learns to know his owner soon. He loves his owner, even after his owner loses his life. Here's a story about such a horse. In a war, the owner passed away(死), and fell from his horse. When people found his body some days later, the horse was still standing beside it. During that long time, the horse didn't leave the body of his owner, without food or water, in the coldest weather, driving away the birds that might eat it. Wasn't he a great animal?

在做“验证力的平行四边形定则”的实验中，下列正确的是(　　)

长方体的六个面中最多只有四个面的面积相等。(   )

工农业生产、人类生活与化学有着密切的关系，请从Ca、O、H、Cl、N、S和C七种元素中选择适当的元素并按要求填空：

（1）用适当的数字和符号填空：①三个硫原子____ 　；②两个氯酸根离子____ 

（2）写出符合下列要求物质的化学式：

①能作为燃料的氧化物____ 　；②充入食品包装袋中可防腐的单质____ ；

③农业上改良酸性土壤的化合物　____ ；④能产生温室效应的主要气体____ 　．