A technician is troubleshooting a laptop LCD, and when the cover is opened nothing shows on the screen. Then all of a sudden the screen comes on and works fine. Which of the following should the technician check FIRST?（）

Jill, a technician, is installing several PCs in a home that is pre-wired with Ethernet to seven rooms. In the wiring closet all the Ethernet cables are hanging free and are not labeled.
Which of the following tools would the technician use to locate the cable that runs to each room?（）