注：横线部分可替换
  1. ______is now being questioned by more and more people.
  ______正受到越来越多人的质疑。
  2. Although many people claim that, along with the rapidly economic development, the number of people who use ______are decreasing and ______is bound to die out. The information I've collected over the recent years leads me to believe that ______will continue to play extremely important roles in modern society.
  尽管许多人认为随着经济的高速发展，用______的人数会减少，______可能会消亡，然而，这几年我收集的一些信息让我相信______仍然会继续在现代社会发挥极其重要的作用。
  3. experts point out that increasing______not only causes serious problems such as global warming but also could threaten to end human life on our planet.
  专家指出：持续增加的污染不仅会导致像全球变暖这样严重的问题，而且还将威胁到人类在这个星球的生存。
  4. In view of such serious situation, environmental tools of transportation like______are more important than any time before.
  考虑到这些严重的状况，我们比以往任何时候更需要像______这样的环保型交通工具。
  5. Using______contributes greatly to people's physical fitness as well as______
  使用______有助于人们的身体健康，并______。