Answer:- Option D Calvin cycle
Explanation:-
Photosynthesis occurs in two parts:
1. Light dependent reaction which requires sunlight. In this reaction the energy from sunlight gets absorbed by the chlorophyll and is then converted into chemical energy in the form of NADPH and ATP.
2. Light independent reaction which is also known as the calvin cycle takes place to provide energy to form carbohydrates using the energized electrons that were obtained from the light dependent reactions. Since, they do not require light for their reaction they can also occur during the night.