Concept:Photosynthetic organisms contain chlorophyll, which enables them to manufacture their own food from sunlight.
Explanation:Amoeba and Paramecium are heterotrophic protozoans that feed on other organisms.
Euglena possesses chloroplasts, while Chlamydomonas is a green alga, so both can photosynthesize.
Volvox is photosynthetic, but Rhizopus is a non-photosynthetic fungus.
Nostoc is a photosynthetic cyanobacterium, but Plasmodium is a non-photosynthetic parasite.
Therefore, the only pair in which both organisms are photosynthetic is Euglena and Chlamydomonas.
Answer:B. Euglena and chlamydomonas