The most important energy carriers in all living cells is

The most important energy carrier in all living cells is ATP.

In living cells, ATP is the most significant energy transporter. It is known as adenosine triphosphate. ATP, the major type of chemical energy in all living cells, is the most common source of chemical energy that fuels biological activities. ATP is made up of the nitrogenous base adenine, the five-carbon sugar ribose, and a three-phosphate group chain.

Hence, the correct answer is option D) ATP.