Final answer:
The sequence of diagnostic tests performed when a computer is turned on is the Power-On Self-Test (POST).
Step-by-step explanation:
The succession of built-in diagnostic tests performed when turning on a computer is known as POST, which stands for Power-On Self-Test.
The POST is a series of checks that the computer's Basic Input/Output System or BIOS performs on the hardware components of the computer to ensure they are working correctly before the operating system begins to load. It involves testing the computer's hardware, such as the Random Access Memory (RAM), and making sure that essential peripherals are connected and functioning.
The CMOS (Complementary Metal-Oxide Semiconductor) is not a diagnostic test, but rather a part of the motherboard that stores the BIOS settings powered by a CMOS battery. Therefore, the correct answer is a) POST.