What would you likely find in a typical expansion slot on a motherboard?

In a typical expansion slot on a motherboard, you would find an expansion board. Expansion slots are specifically designed to accommodate additional hardware components that enhance a computer's capabilities, such as graphics cards, sound cards, and network cards. These boards can significantly improve a system's performance by allowing it to handle more tasks or processing needs beyond what the onboard components offer.

Expansion slots are connected directly to the motherboard, which ensures that the installed boards can communicate with the CPU and other hardware efficiently. Thus, the presence of an expansion board within an expansion slot aligns perfectly with the intended use of these slots, making this choice the most fitting in relation to the other options provided.