单项选择题
A. The network connection is unavailable.
B. The printer is offline.
C. The user does not have the proper security permissions.
D. The print spooler is stopped.
单项选择题 Which of the following commands scans and verifies system protected files?（）
单项选择题 Which of the following tools should Mike, a technician, use when testing a serial port?（）
单项选择题 A user would like to use an external monitor with their laptop, but when the monitor is plugged in and connected to the laptop, the screen does not display on the monitor. Which of the following is the BEST way to display an image on both the monitor and the laptop?（）