Explanation:

The correct option is (B) a tablet PC. A processing device is any device that performs operations on data. While the CPU is the primary processing unit, a tablet PC is a complete computing system that inherently contains a CPU and performs extensive data processing as its core function. Among the given options, it is the only one that represents a device whose primary purpose is to process information. Option (A) a magnetic ink reader, (D) scanners, and (E) keyboards are all input devices; their primary function is to capture or enter data, not to process it. Option (C) Special function cards (e.g., graphics cards, sound cards) *contain* processing units (like GPUs or DSPs) and perform specialized processing, but the card itself is an expansion component within a larger system. A tablet PC, as a standalone computer, is a direct example of a device that processes data.