The statement that correctly describes the classification of chemical reactions into different categories is:
"not all reactions fit into one category, and some reactions can fit into more than one category."
This is accurate because many chemical reactions can be classified in multiple ways based on different criteria, such as their reactants, products, and energy changes. For example, a reaction may be classified as both a combustion reaction and a redox reaction simultaneously. Additionally, some reactions may not fit neatly into any single category.