AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
The degree of compression, depth of burial, and duration over millions of years primarily determine which form of coal is produced — greater pressure and time producing higher-grade coal like anthracite.
Source: Conventional Sources of Energy, chapter 5
The passage states coal is found in different forms "depending on the degrees of compression and the depth and time of burial." Examiners expect you to identify degree of compression / depth and time of burial as the single determining factor. Mentioning the progression (peat → lignite → bituminous → anthracite) is not required for 1 mark but citing the factor clearly is essential.