The correct answer is: A. a microprocessor.
A microprocessor is a small computer processor that is used to control the operations of a digital device. It is a type of integrated circuit that contains millions of transistors that are etched onto a silicon wafer. Microprocessors are used in a wide variety of devices, including computers, smartphones, and cars.
A dumb digitizer is a device that converts analog signals into digital signals. It does not have any processing power of its own and relies on an external computer to interpret the data. A smart digitizer, on the other hand, has its own microprocessor and can perform some processing on the data before sending it to the computer. This makes it more versatile and can improve the performance of some applications.
The other options are incorrect because they do not provide the processing power that is necessary to make a digitizer smart. A keyboard is a device that is used to input text into a computer. An electromagnetic coupling is a device that is used to transfer energy between two coils of wire. A scanner is a device that is used to convert images into digital files.
In conclusion, the correct answer is: A. a microprocessor.