What is the hardware component that contains soldered parts and slots for other pieces of hardware that can be removed?

A hard drive is a storage device used to retain data long-term. It does not contain slots for additional hardware components but rather serves as a dedicated space for storing files and programs. While it is crucial for a computer's operation, it does not facilitate the connection of other hardware like the motherboard does.

The system clock is a timing device that regulates the operation of the computer’s components, ensuring they function in sync. It is not a physical component that contains slots or soldered parts for other hardware; rather, it simply provides timing signals necessary for the coordination of processes within the computer.

An expansion bus is a communication system that transfers data between the motherboard and connected devices. While it plays a role in connecting hardware, it does not itself contain soldered parts or slots; rather, it is a pathway for data transfer allowing various components to communicate.