Which statement is true regarding the filter output characteristics?

The statement indicating that "A is a low pass curve and D is a band stop curve" is accurate in describing filter output characteristics. A low pass filter allows signals with a frequency lower than a certain cutoff frequency to pass through while attenuating frequencies higher than that cutoff, resulting in a characteristic response that drops off at higher frequencies. This behavior corresponds to curve A as it typically shows a flat response in the low-frequency range and a decline as frequencies increase.

For the band stop curve, also known as a notch filter, it effectively removes signals in a specific frequency range while allowing frequencies outside this range to pass. This is indicative of curve D, which would demonstrate a reduced response in a particular band of frequencies—hence the "stop" characteristic. By representing both types of filters accurately, this option correctly aligns with the fundamental definitions of filter types in signal processing.

In summary, the identification of curve A as low pass and curve D as band stop reflects the defined behavior of these filter types, highlighting their primary functions in altering signal frequencies.