The correct answer is B: Low-pass filter. When a capacitor is added across the feedback resistor in an op-amp circuit (like the inverting amplifier in Figure E7-3), the circuit becomes a low-pass filter. The capacitor provides frequency-dependent feedback that reduces gain at higher frequencies. At low frequencies, the capacitor has high reactance and doesn't significantly affect the circuit, so the gain is determined by the resistor ratio (RF/R1). At high frequencies, the capacitor's reactance decreases, shunting the feedback resistor and reducing the gain. This creates a low-pass response - low frequencies pass through with full gain, while high frequencies are attenuated. The cutoff frequency depends on the capacitor value and feedback resistor value.