Euglena are protists that move by means of flagella, and they contain chloroplasts and an eye spot or light receptor. they are capable of ingesting food by phagocytosis. being simple organisms, they can reproduce asexually. under what environmental condition would we expect euglena to ingest food rather than produce food via photosynthesis? a) when light is limited b) when light is abundant c) when oxygen is limited d) when temperatures drop

The correct answer is A.
According to the information provided, Euglena are protists which are both heterotrophs and autotrophs. They can ingest food through phagocytosis, which means that they are heterotrophs. However, they contain chloroplasts and a structure acting as a light receptor. This means that Euglena can use light energy to produce chemical energy, through photosynthesis. 

If sunlight is limited, then the photosynthetic process cannot occur and the Euglena will ingest food.