A. (1) ……..using the computer as your hobby can be harmful to both your health and your social life.  (2)……., sitting all day in front of the computer can cause health problems such as eye-tiredness and obesity. Secondly, you may get irritated (3)…….. Besides, if you use the computer too much, you won't have time for your family and friends. (4) In ……., computers should only be used for a (5)…….time.
1.    a. In my opinion,    b. I think that    c. I believe            d. All are correct
2.    a. Firstly    b. Finally    c. Therefore    d. In conclusion
3.    a. easily    b. easy    c. more easy    d. A&B are correct
4.    a. these reasons    b. short    c. reason    d. also
5.    a. limited    b. free    c. unlimited    d. day