Which form is usually not included in a three-movement classical composition? a. minuet and trio b. sonata form c. rondo d. scherzo

D. Scherzo

I'm pretty sure. 

It depends on what type of third separates the three notes.for example: if you have two mayor thirds is an "aumented chord"if you have two minor thirds is an "diminued chord"if you have one mayor first and then one minor is a "mayor chord"and inverted is a "minor chord"