The correct answer is: D. Generally free from problems of non-linearities.
An open-loop control system is a control system in which the control action is generated without considering the process output. This means that the control action is based solely on the input command. Open-loop control systems are less expensive to design and implement than closed-loop control systems, but they are not as reliable. This is because open-loop control systems are not able to compensate for disturbances or changes in the process.
Non-linearities are a type of disturbance that can cause problems in open-loop control systems. Non-linearities can occur due to the physical characteristics of the process or due to the way in which the control system is designed. Non-linearities can cause the control system to become unstable or to produce undesirable output.
Therefore, the statement “Generally free from problems of non-linearities” is not necessarily correct for open control systems.