Which of the following terms is NOT part of a major chord?

A) Tonic

B) Platonic

C) Dominant

Answer: Option B.

Explanation:

In the major chord, the tonic is the "rest" note, this is the root of the chord, for example, in E major, E is the tonic.

Dominant is the note with more "strength" in the chord, is the fifth degree in the chord, for example in the C major chord, the dominant will be G.

Then the correct option is B, platonic.