My eyelids need a firmware upgrade

One of your old file servers is connected to a CRT display, and the screen flickers noticeably when you’re viewing the screen. Which of these is the most likely cause of this flickering?

CompTIA A+ 220-701: 1.7 – Display Devices

We can’t easily use our computers without some type of display device, and you’ve got many to choose from. In this module, you’ll learn about CRTs, display projectors, display connector types, and the specifications you should consider when purchasing a new LCD monitor.