英语四级听力全真模拟题(二)_大学英语听力

英语四级听力全真模拟题(二)

　　Security alarm systems have all been available for many years and have long been common in commercial and industrial establishments and in large homes. But until the last few years, these system were almost always professionally installed because they required complicated wiring techniques, individualized design and sometimes lots of carpentry---all of which made them expensive。

　　To answer the demand for low-cost alarm systems that can be easily installed, several companies now make alarms that are specifically designed as do-it-yourself。 These systems come with detailed installation instructions and usually do not require inside-the-wall-wiring。

　　Questions 29 to 31 are based on the passage you have just heard。

　　29. Which statement is true according to the passage?

　　30. According to the passage, why have security alarm system been expensive for many years?

　　31. Whats the main idea of this passage?

　　Passage Three

　　Around the world more and more people are taking part in dangerous sports and activities. Of course, there have been people who have looked for adventure---those who have climbed the highest mountains, explored unknown parts of the world or sailed in small boats across the greatest oceans. Now, however, there are people who seek an immediate thrill from a risky activity which may only last a few minutes or even seconds。