Which kind of devices allows the user to add components and capabilities to a computer system?

ANS:E - Expansion slots

Alternatively referred to as a bus slot or expansion port, an expansion slot is a connection or port located inside a computer on the motherboard or riser board that allows a computer hardware expansion card to be connected. For example, if you wanted to install a new video card on the computer, you'd purchase a video expansion card and install that card into the compatible expansion slot.