The correct answer is A. Manual control.
Manual control is the control of computer system or subsystem operation by an operator who may intervene at arbitrary times. This means that the operator can manually control the computer system or subsystem, rather than having it run automatically. This can be useful for tasks that require human intervention, such as troubleshooting or repairing a problem.
B. Mapping is the process of associating one set of data with another set of data. This can be used to convert data from one format to another, or to store data in a more efficient way.
C. Shift register is a type of memory that stores data in a linear fashion. This means that the data is stored one bit after the other, and can be accessed in a sequential manner.
D. ALU is the arithmetic logic unit of a computer. It is responsible for performing arithmetic and logical operations on data.
E. None of the above is not a correct answer.