A low-pass filter: A. passes lower-frequency signals and reduces higher-frequency signals B. passes higher-frequency signals and reduces lower-frequency signals C. has no effect on ac signals D. reduces the level of all frequencies by a significant amount E. None of the above

The correct answer is: A. passes lower-frequency signals and reduces higher-frequency signals.

A low-pass filter is a filter that passes low-frequency signals and reduces high-frequency signals. It is a type of electronic filter that removes high-frequency components from a signal while passing low-frequency components. Low-pass filters are used in a variety of applications, such as audio signal processing, video signal processing, and telecommunications.

Option B is incorrect because a low-pass filter reduces high-frequency signals, not low-frequency signals.

Option C is incorrect because a low-pass filter does have an effect on AC signals. It passes low-frequency AC signals and reduces high-frequency AC signals.

Option D is incorrect because a low-pass filter does not reduce the level of all frequencies by a significant amount. It only reduces high-frequency signals.

Option E is incorrect because the correct answer is A.