What is the typical range of an octave?

The typical range of an octave consists of eight notes. This is based on the musical scale, where an octave encompasses the interval from one note to the next occurrence of that same note, either ascending or descending. For example, if you start on a C note, the notes C, D, E, F, G, A, B, and then the next C make up an octave. This includes the starting note as well as the final note that is one octave higher.

Each of the other choices represents a count of notes that does not adequately cover the full span of an octave. For example, if you consider there to be six, five, or seven notes, you would either be omitting some notes or counting incorrectly, as the full structure of an octave is indeed defined by the presence of eight distinct pitches.