Specify which of a good explanation it violates. The standard requires that a good explanation be explanatory, deep, powerful, falsifiable, modest, simple, and conservative. A single explanation might violate more than one standard.
1. Although we usually have class at this time in this room, I don't see anybody in the classroom, because a wicked witch made them all invisible.
2. Although we usually have class at this time in this room, I don't see anybody in the classroom, because they all decided to skip class today.
3. Although we usually have class at this time in this room, I don't see anybody in the classroom, because it's Columbus Day.