Which of the following is NOT a type of motherboard form factor?

The correct answer identifies PGA as not being a motherboard form factor. Instead, PGA, which stands for Pin Grid Array, refers to a type of CPU packaging where the pins are arranged in a grid pattern on the bottom of the processor. This is a method of connecting the CPU to the motherboard, but it does not define the size, shape, or mounting characteristics of the motherboard itself.

In contrast, ATX, ITX, and Micro-ATX are all recognized form factors that dictate the physical dimensions and layout of motherboards. These form factors establish standards for the size of the board, the arrangement of components, and the overall compatibility with cases and power supplies. Understanding these form factors is crucial for system building and hardware compatibility, where factors like space, expansion slots, and component arrangement come into play.