Which best describes the nature of photosynthesis?
a. it is an energy-attracting process.
b. it is an energy-building process.
c. it is an energy-releasing process.
d. it is an energy-storing process.

Photosynthesis can be defined as the process by which some organisms and green plants use the sunlight in order to make their food from the water and carbon-dioxide. The photosynthesis is a energy-storing process as it stores the energy of the sunlight in the form of the bonds of the glucose molecules. These bonds are broken when energy is needed by the cells.

Hence, the correct answer is 'Option D - it is an energy-storing process'.