Concept: Spirogyra is a green alga that makes its own food by photosynthesis.Explanation: Spirogyra contains chloroplasts and performs photosynthesis.Photosynthesis is a type of autotrophic nutrition where organisms use light energy.This form of nutrition, in plants and green algae, is called holophytic nutrition.It does not depend on other organisms for food, unlike holozoic or symbiotic nutrition.It also does not use chemical energy, so chemosynthetic nutrition is incorrect.Answer: D. Holophytic