Answer : 4. "Peat"
Explanation :

Answer: D) Peat Explanation: The first of the four stages of coal formation is lignite coal.   There are four stages of coal formation:   1. Peat,   2. Lignite,   3. Bituminous and   4. Anthracite. The bacteria has removed a large portion of the other constituents of the plant matter and left around 25 to 34 percent.