A group of notes played in succession with a perceivable shape is called a melody. A melody is a sequence of musical notes that are perceived as a single entity. It is the part of the music that you can hum or sing along to. Melodies are often the most memorable part of a song and are typically built from a series of pitches and rhythms that create a recognizable pattern.
In contrast, harmony refers to the combination of different musical notes played or sung simultaneously to produce a pleasing sound. Consonance and dissonance are terms used to describe the quality of the harmony, with consonance being a stable, harmonious combination of notes and dissonance being a tense or unstable combination.
Therefore, the correct answer to the question is a. melody.