Which form of coal has the highest carbon content in it?(a)- Lignite(b)- Sub-bituminous(c)- Bituminous(d)- Anthracite

The form of coal with the highest carbon content is (d) Anthracite.

Explanation:
Coal forms through a process known as coalification, which occurs over millions of years as plant material is buried, subjected to heat and pressure, and transformed into different types of coal. The carbon content increases as the coal matures through this process. The four major types of coal in increasing order of carbon content are:

Lignite: This is the lowest rank of coal, with the least carbon content (around 25-35%). It has a high moisture content and is the least energy-efficient form of coal.

Sub-bituminous: This type has a higher carbon content than lignite (about 35-45%) but is still low in comparison to other forms of coal.

Bituminous: This type contains about 45-86% carbon. It is widely used in electricity generation and has more energy content than sub-bituminous and lignite.

Anthracite: This is the highest rank of coal, containing about 86-98% carbon. It burns more cleanly and has the highest energy content, making it the most efficient coal for heat and power generation.

Since anthracite has the highest carbon content, the correct answer is (d) Anthracite.