单项选择题 A user states that they are trying to project their laptop to a screen for a presentation. They have plugged the projector cable into their laptop, and turned the projector on, but no signal is found. Which of the following should the technician perform FIRST?（）

单项选择题 A user states that whenever they try to launch a certain installed application, they hear unusual whirring/clicking sounds from their machine and the application never loads. Which of the following components would a technician MOST likely need to replace?（）

单项选择题 Which of the following security threats are MOST likely prevented through user training?（）