题目

Researchers have shown that your talent for happiness is, to a large degree, determined by your genes（基因）.                       31___  We can do this by overcoming negative emotions and developing positive emotions. Strategy（策略）1: 32   The first step is to make a choice to be happy. In Seeking Happiness, Bertrand Russell said, “Happiness must be an achievement rather than a gift of the gods, and in this achievement, effort must play a great part. Once you’ve decided to be happier, you can choose strategies for achieving happiness. Strategy 2:关于磁感线的描述，正确的是（　　）A．磁铁的磁感线从N极出发，终止于S极B．利用磁感线疏密程度可定性地描述磁场中两点相对强弱C．磁铁周围小铁屑有规则的排列，正是磁感线真实存在的证明D．不管有几个磁体放在某一空间，在空间任一点绝无两根（或多根）磁感线相交