Explanation: The Intermediate Frequency (IF) section of a receiver contains filters specifically designed to select the desired signal and reject signals on adjacent frequencies. If the IF filter bandwidth is too wide, it allows not only the intended signal to pass through but also other strong signals or noise on nearby frequencies. These unwanted signals will then be amplified and demodulated along with the desired signal, resulting in interference that reaches the audio stage, making the desired signal difficult to hear or understand. This reduces the receiver's selectivity. A) Output-offset overshoot is generally related to amplifier design or control systems, not directly to IF bandwidth. C) While a wider bandwidth *does* admit more thermal noise, "undesired signals" (meaning other radio transmissions) are a more significant and specific problem addressed by IF filter selectivity. D) Filter ringing is typically associated with very narrow or sharply selective filters, especially those with steep skirts, not overly wide ones.