I found that the most obvious cause of happiness is intense concentration. This must be the main reason why activities such as music, art, literature, sports and other forms of leisure have survived. In order to concentrate, whether you're reading a poem or building a sandcastle, what you need is a challenge that matches your ability. The way to remain continually happy, therefore, is to keep finding new opportunities to improve your skills. This may mean learning to do your job better or faster, or doing other more difficult jobs. As you grow older, you have to find new challenges which are more appropriate to your age.

　　语篇解读：本文是记叙文。作者经过研究发现人的幸福感来源于做事情的专注度。

　　24．What led the author to study psychology?

　　A．His determination to become rich.

　　B．His observation of adults.

　　C．His unhappy childhood.

　　D．His interest in strangers.

　　解析：选B　推理判断题。第一段提到作者小时候看到周围富有且受过教育的成年人并不快乐，因而决定找到使人们获得快乐的途径，由此可推断：他对成年人的观察促使他学了心理学。

　　25．Who were the author's study subjects at the start of his career?

　　A．People having deep affection for their career.

　　B．People very aware of their personal life.

　　C．People successful in acquiring wealth.

　　D．People with more freedom.

　　解析：选A　推理判断题。由第二段中的"I started out by studying ... who devoted their lives to doing what they wanted to do"可知，作者认为他选择的研究对象是热爱自己事业的一群人。

　　26．The author used his system to show that ________.

　　A．people's happiness depends on who they are with

　　B．people are happier when they focus on an activity

　　C．creative people are happier than ordinary people

　　D．ordinary people find it hard to concentrate

　　解析：选B　细节理解题。由第三段中的"as with creative people, ordinary people are happiest when concentrating hard"可知，作者采取经验取样法研究发现：普通人和有创造性的人一样，他们在集中精神做事情的时候最快乐。

　　27．According to the text, people concentrate most when they are doing ________.

　　A．something strange and enjoyable

B．something difficult but possible