To understand what happens to the gain of a non-inverting amplifier using an OP-AMP when the feedback resistor value is increased, we need to look at the gain formula for such a configuration.

The gain \( A_v \) of a non-inverting amplifier is given by the formula:

\(A_v = 1 + \frac{R_f}{R_{\text{in}}}\)

where:

• \(R_f\) is the feedback resistor connected between the output and the inverting input.
• \(R_{\text{in}}\) is the resistor connected between the inverting input and the ground.

If the feedback resistor \( R_f \) is increased by 5% while keeping the input resistor \( R_{\text{in}} \) constant, let's see how the gain changes:

- Initial value of feedback resistor: \(R_f\)

- Increased value of feedback resistor: \(R_f' = R_f + 0.05 R_f = 1.05 R_f\)

Substituting the new feedback resistor value into the gain equation gives:

\(A_v' = 1 + \frac{1.05 R_f}{R_{\text{in}}} = 1 + \frac{R_f}{R_{\text{in}}} + \frac{0.05 R_f}{R_{\text{in}}}\)

The expression \(\frac{0.05 R_f}{R_{\text{in}}}\) shows that the gain \(A_v'\) is greater than the original gain \(A_v\).

Therefore, when the feedback resistor is increased by 5%, the overall gain of the non-inverting amplifier increases.

Thus, the correct answer is: The gain increases.