Answer: C. LED module.
Answer analysis: When discussing the basic building blocks of LED displays, we need to understand how LED displays are built and work. Now, let's analyze each option one by one:
A. LED pixel: Although the LED pixel is the basic element that constitutes the image, it does not exist as an independent, replaceable or identifiable unit in the architecture of the LED display. LED pixel usually refers to a unit composed of multiple LED lamp beads (red, green, blue or other colors) to display a single color or brightness point. However, when discussing the "basic building blocks" of the display, we usually do not regard the pixel as an independent, removable unit.
B. LED cabinet: The LED cabinet is a frame that multiple LED modules are assembled together, which provides mechanical support and protection. However, the cabinet is not the basic unit of the display to display content or images, but a larger structure composed of multiple modules.
C. LED module: The LED module is the basic building block of the LED display. It consists of multiple LED pixels (or LED lamp beads) packaged on a circuit board or substrate in a certain arrangement, and is equipped with necessary driving circuits and protection measures. Modules are the smallest, independently working units in LED displays. They can be manufactured, tested and replaced individually, and are the basis for the entire display screen.
D. Power supply: The power supply is an important part of the LED display and is responsible for providing power to the display. However, the power supply is not the "basic component unit" of the display, but the device that provides energy for it.
In summary, the basic component unit of the LED display is the LED module, because they exist in the smallest, independently working form and together constitute the entire picture of the display. Therefore, the correct answer is C. LED module.