If two sounds vary in frequency,what will be the nature of the perceptual difference

A)  loudness
B)  timbre 
C)  decibels
D)  pitch

Perceptual Difference

Variations in the way individuals interpret or perceive sensory information, often influenced by their unique experiences and physiological factors.

Frequency

In general terms, the rate at which something occurs over a particular period of time or in a given sample.

Pitch

The perception of the frequency of sound, determining how high or low a tone sounds.