To understand why increasing the input can reduce the steady-state error, let's first define what steady-state error is. In control systems, steady-state error refers to the difference between the desired output and the actual output of a system after it has reached a stable condition. It indicates how well the system is tracking the desired response or following the given input.

The steady-state error is influenced by various factors, such as the type of the system, system gain, and static error constant. However, in this question, the correct answer is option 'D' - by increasing the input. Let's explore why this is the case.

When the input to a control system is increased, it directly affects the output of the system. By increasing the input, the system is driven to produce a larger output response. This can help reduce the steady-state error as the system tries to match the increased input with a higher output.

Here's a detailed explanation of why increasing the input can reduce the steady-state error:

1. Relationship between input and output:
- In a control system, the output is determined by the input and the system's transfer function or characteristics.
- Increasing the input increases the magnitude of the output response of the system.

2. Steady-state error and input-output relationship:
- The steady-state error is the difference between the desired output and the actual output.
- By increasing the input, the output of the system tends to increase as well.
- As the output gets closer to the desired output due to the increased input, the steady-state error decreases.

3. Importance of system linearity:
- The reduction in steady-state error by increasing the input is more effective in linear systems.
- Linear systems exhibit a proportional relationship between the input and output.
- In such systems, the steady-state error decreases linearly with the increase in input.
- Nonlinear systems may not exhibit the same behavior, and the relationship between input and output can be more complex.

4. Saturation and limitations:
- It's important to consider the limitations of the system when increasing the input.
- If the output of the system reaches its maximum limit or saturation point, further increasing the input may not reduce the steady-state error.
- Saturation occurs when the system output cannot increase beyond a certain value, regardless of the input magnitude.

In summary, increasing the input can help reduce the steady-state error by driving the system to produce a larger output response. However, it is essential to consider the limitations and linearity of the system to ensure the effectiveness of this approach.