Final answer:
Built-in memory or primary storage in a computer system is referred to as RAM, which stands for Random Access Memory.
Step-by-step explanation:
The term for built-in memory or primary storage in a computer is RAM, which stands for Random Access Memory. It is a volatile type of storage that temporarily holds data and instructions that the CPU needs to access quickly. Unlike ROM (Read-Only Memory), which is non-volatile and contains data that does not change, RAM data is lost when the computer is turned off. On the other hand, SSD (Solid-State Drive) is a type of non-volatile storage typically used as secondary storage. Lastly, cache is a small amount of faster memory that's used to store frequently accessed information temporarily, to improve processing speed. However, when referring specifically to primary, built-in memory, the correct answer is b) RAM.