题目

如图所示为固定在桌面上的“C”形木块，abcd为光滑圆轨道的一部分，a为轨道的最高点，de面水平．将质量为m的小球在d点正上方h高处释放，小球自由下落到d处后沿切线进入圆形轨道运动，则（     ） A．在h一定的条件下，释放后小球能否到a点，与小球质量有关 B．改变h的大小，就可使小球在通过a点后落回轨道之内，或者落在de面上 C．要使小球通过a点的条件是在a点的速度v>0 D．无论怎样改变h的大小，都不可能使小球在通过a点后又落回轨道内  The first reality TV show in the world was called Expedition Robinson and it was shown in Sweden in 1997. Half the population of the country watched the final event and a new kind of TV program was born. Two years later in Holland , the first series of Big Brother was filmed. Again, it was a great success and the final program was watched by 15 million people. Now more than 20 countries around the world have Big Brother or Expedition Robinson on their TV screens. The ordinary people who take part in the programs are known by millions of people in their own countries and reality TV has become big, big business.   For the TV producers, reality TV is a dream come true because many of the programs cost nothing to make. At some point, the television viewers are asked to telephone the program to vote or to apply to take part in the show. It is the cost of these telephone calls that pays for the shows. One of the most popular shows is Pop Idol. In the show a group of attractive young people are made into pop stars. TV viewers vote for their favorite person on the show. The winner makes a record and millions of copies of the record are sold. His or her pictures are published on the covers of magazines or on the front pages of newspapers, and then, they are quickly forgotten.    But not everyone is happy about reality TV. In Portugal, two TV channels got into trouble because they showed too much of the personal lives of the people in the shows. In France, reality TV is called “rubbish TV” and the TV studios of Big Brother were attacked three times in one week. In Greece, Big Brother was described as “ against human rights and civilization”. 1. Those who take part in the reality TV shows are usually _____.   A. common people     B. pop TV stars   C. attractive people    D. famous film stars   2. Who would pay for the cost of the reality TV shows according to the passage?   A. TV producers who make reality TV shows   B. TV actors who take part in reality TV shows.   C. TV viewers who telephone reality TV shows   D. TV companies which broadcast reality TV shows 3. Which of the following statements is NOT true according to the passage?    A. Pop Idol is one of the popular reality TV shows in the world.    B. Big Brother was one of the first reality TV shows in the world. C. Rubbish TV is one of the personal reality TV shows in the world. D. Expedition Robinson was the first reality TV shows in the world. 4. It can be concluded from the passage that ______.  A. everyone is happy about reality TV.  B. reality TV will do well in many countries.  C. all the people in Europe are in favor of reality TV    D. reality TV will not be broadcast in any countries.