Other than C, an alternative answer would be A. That's because a Perfect Octave consists of 8 notes (meaning that a note with the octave is the same, just different pitches). This is because the notes A, B, C, D, E, F, G are all continuously repeating until the highest note. Even though the notes repeat doesn't necessarily mean the pitch and height of the note are the same. It's pretty similar between these two options, but be sure to distinguish the two.
