1. ______is now being questioned by more and more people.
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.
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.
4. In view of such serious situation, environmental tools of transportation like______are more important than any time before.
5. Using______contributes greatly to people's physical fitness as well as______.
6. Despite many obvious advantages of______, it is not without its problem.
7. ______is more than just an electronic appliance; it is a means of expression, as well as a vehicle for communication, and as such becomes a powerful tool for reaching other human beings.
8. From what has been discussed above, we may safely draw the conclusion that advantages of ______far outweigh its disadvantages and it will still play essential roles in modern society.
9. There is a general discussion these days ______over in many colleges and institutes. One of the questions under debate is whether ______is______.