Photosynthesis is
1.the process by which certain microorganisms create organic molecules from inorganic nutrients
2.the use of chemical energy to convert water and carbon dioxide into energy-rich glucose molecules
3.the use of light energy to convert water and carbon dioxide into energy-rich glucose molecules

The correct answer for the blank is-

3) The use of light energy to convert water and carbon dioxide into energy-rich glucose molecules.

Photosynthesis is process of formation of food ( glucose) in green plants and algae using carbon dioxide and water in the presence of sunlight.

In the first phase ( a light dependent phase), a green pigment called chlorophyll ( present in the chloroplast of plants and algae) first absorbs the energy from sunlight and converts it into chemical energy in the form of ATP, and NADPH.

This energy is then utilized in the formation of energy rich glucose molecule in the next phase, which is a light independent phase.

Thus, option 3) is the right answer.

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