问题 读图填空题

如下图所示的实验中,甲、乙两个瓶中都装有澄清石灰水。在吸入气体时,左手捏紧橡皮管,右手松开。在呼出气体时,右手捏紧橡皮管,左手松开。请回答:  

(1)甲瓶中的浑浊程度________,说明吸入的空气中______的含量较______;乙瓶的浑浊程度________,说明呼出的气体中的_______含量较_______。

(2)甲瓶在这个实验中起_________作用。

(3)由实验可见,呼出的气体中_________的含量减少,_______的含量增加。这种变化是因为在人体的_______和_______的周围发生气体交换的缘故。

答案

(1)不明显;二氧化碳;低;明显;二氧化碳;高  

(2)对照 

(3)氧气;二氧化碳;肺泡;毛细血管

选择题
问答题

Libraries form a vital part of the world’s systems of communication and education.
They make available knowledge accumulated through the ages. People in all walks of life use library resources in their work. People also turn to libraries to satisfy a desire for knowledge or to obtain material for leisure-time activity. In addition, many people enjoy book discussions, concerts, film programs, lectures, story hours, and a variety of other activities provided by libraries. Libraries also play an important role in preserving a society’s cultural heritage(遗产). The library ranks as one of society’s most useful service institutions.
The contents of libraries have changed so much through the years that the word library itself is, in a sense, inaccurate. The word comes from the Latin word liber, which means book. Today’s libraries house many books, of course. However, they also have a wide variety of other materials that communicate, educate, and entertain. These materials include magazines, manuscripts (手稿), newspapers, and computer documents.
Audio and visual materials include CDs, audiocassette tapes, videotapes, films, maps, paintings, and photographs.
In addition to regular books, a library may have large-type books, books for the blind, and tape recordings of books, called talking books. Librarians keep pace with the changing contents of libraries to serve as many people as possible. Their efforts have turned libraries into multimedia resource centers.
The expansion of library contents greatly increases the library’s ability to communicate and educate. For example, people interested in classical music can listen to CDs and read books on the topic. Students of agriculture can read magazines and watch videotapes on farming methods. Many people use magazines and newspapers to find the most up-to-date material on current events.
In addition to expanding contents, librarians have developed many kinds of libraries to serve the needs of different people. The materials of each kind of library are selected to meet the needs of a specific group of patrons. School libraries have collections that provide the information needed by elementary and high school students. Public libraries tailor their collections to the general public. Government library collections are geared chiefly toward serving the needs of government officials. Thousands of special libraries provide information for professional people, such as advertising specialists, bankers, editors, engineers, lawyers, physicians, and scientists.