9. Paper was invented by the Chinese a long time ago.
10. The first phone with touch screen was released by IBM in 1993.
11. The earth has been protected from ultraviolet r rays by the ozone layer.
12. To improve Josh's muscles, he goes to the gym twice a week.
13. To get the first prize in the singing contest, Hung practices singing every day.
14. In order to contribute to protecting the environment, we should carry our own bags to the markets.
15. To use the computer effectively, you should be aware of both its advantages and its disadvantages.
- $Answered_{}$ $by_{}$ $thieukhue_{}$ -
