Answer
a. light absorption
Work Step by Step
A photosynthetic reaction is triggered by absorption of light. Without light, photosynthesis cannot occur, which is why many plants die without sunlight.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.