Explanation: Butterworth filters are renowned for their "maximally flat" passband response (C). This means the gain or attenuation is as constant as possible across the desired frequency range, with no ripples, before it begins to roll off smoothly. This characteristic is achieved by carefully placing the poles of the filter's transfer function on a circle in the s-plane. Option A describes a *constant-k* filter, an older filter design approach based on image parameters, not a Butterworth filter. Options B and D are incorrect because most practical, high-performance filters, including Butterworth designs, utilize both inductors and capacitors (LC components) to achieve their frequency-selective properties. Filters composed solely of capacitors or inductors would be limited in their response and performance.