vessels (血管)．Your kidneys (肾) must work overtime to get rid of extra water out of your system.Your kidneys are not a pair of pipes.Flushing more water through your kidneys doesn't necessarily help it become cleaner.Rather, your kidneys can get damaged by unnecessary wear and tear over time.And drowning your system with large amounts of water is one of many potential causes of kidney damage.

　　Putting unnecessary stress on your system and your kidneys by consuming unnecessary water is an unnoticeable process.For the average person, it is usually impossible to know that this stress exists, as there are usually no obvious symptoms on a moment­to­moment basis.But make no mistake about it: this stress is real and can hurt your health over the long term.

　　语篇解读：本文为说明文。过量饮水对我们的健康危害很大，我们应该避免过量饮水。

　　4．Why is the Californian woman mentioned?

　　A．To lead to the topic of the text.

　　B．To tell us a tragic news story about a mother.

　　C．To tell us it can be dangerous to take part in contests.

　　D．To tell us how much water we can drink at most one time.

　　解析：选A　推理判断题。本文主要是讲过量饮水对身体有害，而提到那个加州女人的故事是为了引出这个话题。

　　5．When the participants showed signs of pains, the organizers ________.

　　A．became very concerned

　　B．were laughed at by others

　　C．tried to reduce their pains

　　D．didn't pay much attention to them

　　解析：选D　推理判断题。由第一段"When she and other participants complained of ...laughed at by the organizers."可知，那些组织者并没怎么在意他们。

6．What's the main idea of Paragraph 3?