Section B Directions: In this section, you will hear 3 short passages. At the end of each passage, you will hear some questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A, B, C and D. 听力原文： The use of silicon is basic to the developments which have taken place since the 1950s. This element has special electrical properties. It is a semiconductor, half way between a full conductor such as copper and an insulator like plastic. By adding small amounts of other chemicals to pieces of silicon and then joining the resulting different types together in various ways, a very fast, efficient 'switch' can be produced. As manufacturing processes grew more and more sophisticated, it became possible to pack more and more individual transistors onto a single piece of silicon called chip. These chips are at most 1 centimeter square and a fraction of a millimeter thick. In 1960 a chip could hold one transistor. Today it can contain as many as a million. Silicon chips are changing our world at an enormous pace. They affect or will affect all aspects of our lives—industry, transportation, finance, education, medicine, communication, domestic and recreational spheres. By using micro-technology, computers can now be made with an almost infinite operational capacity. The cost is actually decreasing while their speed of operation is increasing. Their micro-components will last indefinitely under normal conditions. (27)