ANS:C - is a two position control (fully open or fully closed) control adequate to control a process with slow reaction and minimum dead time or transfer lag.

On-off control is a control strategy where the final control element (such as a valve or a pump) is either fully open or fully closed based on the deviation of the measured variable from the set point. Among the options provided: On-off control is a two-position control (fully open or fully closed) control adequate to control a process with slow reaction and minimum dead time or transfer lag. Explanation:

1. Fully opens the final control element when the measured variable is below the set point: This is partially correct, as in on-off control, the final control element will be fully opened when the measured variable is below the set point. However, this statement alone does not fully describe the on-off control strategy.
2. Fully closes the final control element when the measured variable is above the set point: This is partially correct, as in on-off control, the final control element will be fully closed when the measured variable is above the set point. However, this statement alone does not fully describe the on-off control strategy.
3. Is a two-position control (fully open or fully closed) control adequate to control a process with slow reaction and minimum dead time or transfer lag: This statement accurately describes the characteristics of on-off control. On-off control is suitable for processes with slow response and minimum dead time because it operates in a binary manner, fully opening or fully closing the final control element based on the deviation of the measured variable from the set point. It is simple and often used in applications where precise control is not required or where the process dynamics are relatively slow.