The correct answer is option D: The effect of parameter variation and internal noise is less.

Explanation:
An open loop control system is a type of control system where the control action is independent of the output. In other words, the control action is predetermined and does not consider the actual output or the desired output. The control action is based solely on the input or reference signal.

Highly affected by non-linearities:
One of the characteristics of an open loop control system is that it is highly affected by non-linearities. Non-linearities refer to deviations or changes in the system behavior that are not proportional to the input signal. These non-linearities can cause inaccuracies in the system performance.

Open loop systems are inaccurate:
Another characteristic of an open loop control system is that it tends to be inaccurate. Since the control action is independent of the actual output, any disturbances or changes in the system will not be compensated for. This can lead to inaccuracies in the system response and performance.

These are not reliable:
Open loop control systems are also not considered reliable. Since there is no feedback mechanism to correct errors or disturbances, any changes in the system or its environment can significantly affect the system's performance. This lack of reliability makes open loop control systems unsuitable for applications where accuracy and stability are critical.

The effect of parameter variation and internal noise is less:
However, the statement in option D is not true. In an open loop control system, the effect of parameter variation and internal noise is not less. In fact, parameter variation and internal noise can have a significant impact on the system's performance. Without a feedback mechanism to correct for these variations and noise, the system's response can be greatly affected, leading to inaccuracies and instability.

In conclusion, the statement in option D is not true. Parameter variation and internal noise have a significant effect on the performance of an open loop control system.