Which of the following life processes releases energy required for body functions?

The correct option is D. Respiration.

1. Respiration is the process in which the nutrients inside the cell are oxidized to produce energy in the form of ATP.
   
2. The glucose present in the cell is converted to carbon dioxide and water along with the generation of energy inside the cell.
   
3. This energy is used for other biochemical processes in the cell. ​

Nutrition and Digestion:

1. Digestion is the process of breakdown of nutrients which are absorbed by the system. ​​
2. After absorption, the nutrients move towards the cell where it is either stored or used up for specific cellular functions.
3. The process of gaining nutrients from food is called nutrition.

Reproduction:

1. ​Reproduction is the process of development of the next generation of individuals.
   
2. It is not related to release of energy in the system.