Final answer:
The correct answer is a) octave. An octave is the interval between a note and its first overtone that is exactly double the frequency of the original note.
Step-by-step explanation:
The correct answer is a) Octave.
An octave is defined as the interval between a note and its first overtone that is exactly double the frequency of the original note. In other words, when a note is played and its first overtone is produced, the frequency of the overtone will be twice the frequency of the original note, resulting in an octave interval.
For example, if the original note has a frequency of 440 Hz, the frequency of its first overtone (or second harmonic) will be 880 Hz, creating an octave.