导线不经过用电器而直接跟电源两极连接的电路叫____，它的危害是：____．

在工业上，精炼铜、镀铜以及制取各种铜的化合物时，常用到硫酸铜。某工厂用硫化铜(CuS)生产硫酸铜，提出了以下两个生产方案：

方案I：硫化铜在硫杆菌的作用下跟空气中的氧气发生反应，生成硫酸铜，反应方程式为：CuS+2O₂ CuSO₄；

方案Ⅱ：高温煅烧硫化铜，生成氧化铜；氧化铜跟硫酸反碰生成硫酸铜。根据上述信息，请你回答：

B

    Running is becoming popular these days. Many of us run for our health. Doctors say many of the health problems come from these bad habits: eating too much, drinking too much, smoking, and not taking enough exercise. Doctors tell us, "Eat and drink less, don't smoke, and exercise more."

    Running is a good form of exercise because it helps build a strong heart. It also helps most people lose weight. One 68­year­old woman runs three times a week. She runs to lose weight.

    Running is good for health in other ways, too. Many runners say running keeps colds and other small health problems away." Running is my doctor, "says one man.

    Running can also help people to relax. So today men and women of all ages enjoy running.