Explanation:

Coal is classified into different types based on its carbon content, moisture, and calorific value, which determine its commercial utility. \nOption A: 'Peat' is the lowest grade of coal, formed from partially decayed vegetation. It has a very high moisture content and low carbon content, resulting in low calorific value. It is rarely used for large-scale commercial purposes due to its inefficiency. \nOption B: 'Lignite' (also known as brown coal) is a low-rank coal with higher carbon content than peat but still relatively high moisture. It has a moderate calorific value and is used in power generation, but less extensively than higher-grade coals. \nOption C: 'Bituminous' coal is a medium-rank coal, characterized by high carbon content (typically $\text{45-86\%}$) and lower moisture. It has a high calorific value and is the most abundant and widely used type of coal globally for electricity generation, steel production (as coking coal), and various industrial applications. Therefore, this option is correct. \nOption D: 'Anthracite' is the highest rank of coal, with the highest carbon content (over $\text{86\%}$) and lowest moisture. It has the highest calorific value and burns cleanly with little smoke. However, it is relatively rare and harder to mine, making it less popular for general commercial use compared to bituminous coal, though it is highly valued for specific applications like domestic heating. \nTherefore, bituminous coal is the most popular and commercially utilized type due to its balance of abundance, energy content, and ease of use.