Which of the following organic compounds is the main source of energy for living things

yes carbohydrate and fats are the main source of energy in all living things almost.

as we know plants store food in form of starch and animals in the form of glycogen both are carbohydrates. they can easily be formed and also broken down to give instant energy in the form of ATP.

Fats are another source which is used as a long term storage and used when there is a need of ATP in fast or starvation.

A. Carbohydrates. While lipids do store energy, carbohydrates provide fast, immediate energy for living things.