Answer: The correct answer for the blank is- water.
Photosynthesis is a process of formation of food (carbohydrate, which is glucose) by green plants and algae.
In this process, carbon dioxide and water are utilised in presence of sunlight to convert the solar energy into chemical energy (ATP and NADPH), which is finally used in the formation of carbohydrate (glucose).
A closed circuit doesn't allow the flow of electrons. an open circuit does. example: if you turn off a switch in your house. you 'broke the circuit it is closed.
