5Final answer:
The order of grades of coal from lowest to highest energy content is lignite, sub-bituminous, bituminous, anthracite.
Step-by-step explanation:
The correct order of grades of coal from lowest energy content to highest energy content is lignite, sub-bituminous, bituminous, anthracite. Lignite has the lowest energy content as it is young and has a high oxygen content. Sub-bituminous coal comes next in terms of energy content, followed by bituminous coal. Anthracite, the highest grade of coal, has the highest energy content and is a rare find today.