1. I never changed the motherboard2. He bought a new mobile phone this week and all the time playing with him3. We have not yet studied this device4. Last Tuesday we listened to a lecture on the computer's memory5. Why did not you answer the question of the teacher in the previous lesson?6. I have not seen Mary this week7. You have studied computer input device?8. I just replaced the hard drive, is now working on the computer a pleasure9. I have just discussed the purchase of a new computer with parents10. I did not repeat this poem last week11. The teacher spoke about the output device, and now I'm writing a paper on the different types of printers12. I just installed an anti-virus program on your computer13. You have already viewed the e-mail? I sent you a letter yesterday14. Last Wednesday, the lesson we listened to a lecture on new applications15. I bought a new i-background last week16. When you're finished reading this book?17. He did not like the lecture, he did not write for a teacher18. You have finished the discussion? Let's continue with the lesson.19. Did you see Anna today?20. The teacher has not come yet, we are waiting for him.