In a major scale, fourths, fifths, and octaves are defined by what term?

A. major second
B. minor second
C. perfect interval
D. accidental interval

C. perfect interval

The correct answer is C. perfect interval.

To understand why the answer is C, it's important to have a basic understanding of intervals in music theory. An interval is simply the distance between two pitches. In the context of a major scale, the fourth, fifth, and octave intervals have specific characteristics that differentiate them from other intervals.

The fourth is called a perfect fourth because it spans four diatonic scale degrees in a major scale. For example, in the C major scale (C, D, E, F, G, A, B, C), the fourth note is F. The interval from C to F is a perfect fourth.

Similarly, the fifth is called a perfect fifth because it spans five diatonic scale degrees in a major scale. In the C major scale, the fifth note is G. The interval from C to G is a perfect fifth.

Lastly, the octave is also considered a perfect interval. It is called an octave because it spans eight diatonic scale degrees in a major scale. In the C major scale, the octave note is also C. The interval from C to C (octave) is a perfect octave.

Therefore, the correct term to describe these intervals in a major scale is a "perfect interval." So the answer to the question is C. perfect interval.