The correct answer is: A. absolute
Absolute instruments are used to measure the true value of a quantity, without any reference to other quantities. They are typically used in laboratories as standardizing instruments, to calibrate other instruments.
Indicating instruments, on the other hand, are used to indicate the value of a quantity, but they do not necessarily provide an accurate measurement. They are often used in industrial settings to provide a rough indication of a process variable.
Recording instruments are used to record the value of a quantity over time. They are often used in scientific and engineering applications to monitor changes in a process.
Integrating instruments are used to integrate the value of a quantity over time. They are often used to measure the total amount of a substance that has flowed through a pipe or the total amount of energy that has been used by a machine.
None of the above options is correct.