Answer:
a. some carry out photosynthesis through the chloroplasts they incorporate into their cells.
Step-by-step explanation:
Elysia chlorotica is a marine mollusk. Also called sea slug, it feeds on yellow-green algae, Vaucheria. The slug retains the chloroplasts from the algal cells and inserts them into the cells of the lining of its digestive tract.
The presence of chloroplasts allows these cells to absorb the sunlight and perform the photosynthesis to produce glucose. Therefore, incorporation of chloroplasts from their food algae allows the otherwise heterotrophic sea slug to perform the process of photosynthesis.