C

Step 1: We know that for an ideal gas, applying the Ideal Gas Law, we have \( PV = nRT \).
Step 2: When a small change in pressure \( \Delta P \) is applied at constant temperature, we can relate the change in volume \( \Delta V \) by the following:
\( \Delta V = \frac{nR}{P} \Delta P \).
Step 3: In the second scenario, when the temperature is reduced by a small quantity \( \Delta T \) at constant pressure, we can use the relationship derived from the ideal gas law with temperature change, given:
\( |\Delta T| = C |\Delta P| \), where C is a constant.
Step 4: For constant pressure and using the same \( n \) and \( R \), this leads to: \( \Delta V = \frac{nR}{P} \Delta T = \frac{nR}{P} C \Delta P \).
Step 5: The equality of changes in volume gives us the relationship with respect to the constants, confirming the statement of the problem.
Thus, with the given values and relationships established in Step 4, we can conclude the change in volume is quantified using option (C).