当今社会主义中国，全社会、全民族的核心价值导向是（　　）

①富强、民主、文明、和谐  ②自由、平等、公正、法治

③爱国、敬业、诚信、友善  ④互利、共赢、互助、共享

用电源、灯泡、导线、开关和钨丝组成如图所示的电路，闭合开关，小灯泡发光；再用酒精灯对钨丝加热，会发现灯泡亮度变暗，原因是钨丝____ 。

阅读理解

C

     Readingcan be a social activity. Think of the people who belong to book groups. They choose books to read and then meet to discuss them. Now, the website BookCrossing.com turns the page on the traditional idea of a book group.

      Members go on the site and register the books they own and would like to share. BookCrossing provides an identification number to stick inside the book. Then the person leaves it in a public place, hoping that the book will have an adventure, traveling far and wide with each new reader who finds it.

    Bruce Pederson, the managing director of BookCrossing, says, “The two things that change your life are the people you meet and books you read. BookCrossing combines both.”

    Members leave books on park benches and buses, in train stations and coffee shops. Whoever finds their book will go to the site and record where they found it.

    People who find a book can also leave a journal entry describing what they thought of it. E-mails are then sent to the BookCrossing to keep them updated about where their books have been found. Bruce peterson says the idea is for people not to be selfish by keeping a book to gather dust on a shelf at home.

    BookCrossing is part of a trend among people who want to get back to the “real” and not the virtual(虚拟). The site now has more than one million members in more than one hundred thirty-five countries.