单项选择题 A user reports that their machine seems to be running slower than usual. The user states that the computer has become progressively worse as more applications are installed. Which of the following is the FIRST step the technician should take?（）

单项选择题 A laser printer keeps displaying, ‘Paper Jam – Front Door’. It does not matter which tray or paper type the printer is using. Which of the following is the MOST likely reason why the printer is having this issue?（）

单项选择题 A virus has been removed from the user’s machine, but the user still cannot access the Internet.Which of the following should the technician check NEXT?（）