单项选择题
A. A network cable is vibrating against the system case.
B. An internal wire is improperly routed and is hitting the CPU fan.
C. The thermal grease on the CPU has dried out and needs to be replaced.
D. The CPU needs to be reseated.
单项选择题 Which of the following is the BEST tool to troubleshoot a DB-9 port?（）
单项选择题 A laser printer displays ‘perform user maintenance’. The manufacturer’s information was not available when the user performed the maintenance, and the laser printer continues to display the maintenance code. Which of the following items needs to be performed?（）
单项选择题 A technician has just installed a new power supply into a desktop computer and now the computer will not turn on. Which of the following is the MOST likely cause?（）