Final answer:
Fossil fuels are still widely used for their A) energy content, B) cost-effectiveness, and C) availability.
Step-by-step explanation:
The reasons why fossil fuels are still widely used are A) Energy content: Fossil fuels have high energy density and provide a lot of energy when burned making them an efficient source of energy. B) Cost: Fossil fuels are relatively inexpensive compared to other energy sources such as renewable energy. C) Availability: Fossil fuels are abundant and readily available in many parts of the world.