Fill in the following blanks with suitable words:
b) Coal contains mainly ……….

Explanation

To fill in the blank for the question "Coal contains mainly ……….":

1. **Understanding Coal**: Coal is a type of sedimentary rock that is primarily used as a fuel source. It is formed from the remains of ancient plants and is found in various forms, such as anthracite, bituminous, sub-bituminous, and lignite.

2. **Composition of Coal**: The key component of coal is its chemical composition. The primary element that makes up coal is carbon. While coal may contain other elements and compounds, carbon is the most significant one.

3. **Filling in the Blank**: Given that coal is predominantly made up of carbon, we can fill in the blank as follows: "Coal contains mainly **carbon**."

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