A sequence of pitches occurring one after another is perceived: A. horizontally B. vertically C. texturally D. mechanically

Option A is correct.

A sequence of pitches occurring one after the other is perceived horizontally.

Explanation:

This question belongs more to the field of music.

Pitch is a perceptual property of sounds that allows their ordering on a frequency-related scale.

A sequence of pitches is called Scales. A scale is a sequence of pitches, usually listed in increasing order, starting at some initial pitch called the tonic.

Although, pitches in single form are perceived in high and low form (vertical format), when pitches are arranged in sequences as scales occurring one after the other, they are perceived horizontally!