what is meant by percentage of their final consumption of coal has reduced irrespective in increase in direct consumption of total volume of coal?which fuel is most widely used(commercial)?

In response to the first part of your query, a similar question has already been answered. Follow the given link to view the same.

https://www.meritnation.com/ask-answer/question/please-explain-this-statement-among-the-commercial-sources/unit-iii-infrastructure/9779385

In response to the second part of your query, oil is the most widely used commercial source of energy.