The correct answer is: A. eight bidirectional lines that are used to transfer 8 bits between the microprocessor and its I/O and memory.
The data bus is a group of eight bidirectional lines that are used to transfer 8 bits between the microprocessor and its I/O and memory. The data bus is used to transfer data between the microprocessor and the memory, as well as between the microprocessor and I/O devices. The data bus is a group of eight lines, each of which can carry one bit of data. The data bus is bidirectional, which means that it can be used to transfer data in both directions. The data bus is a very important part of the microprocessor, and it is used in many different operations.
Option B is incorrect because the data bus is only eight lines long, not sixteen. Option C is incorrect because the data bus is bidirectional, not unidirectional. Option D is incorrect because the data bus is used to transfer data between the microprocessor and its I/O and memory, not among the registers. Option E is incorrect because the data bus is a group of eight bidirectional lines, not none of the above.