The correct option is D plants and animals
Euglena is a single-celled eukaryote placed under Protista. It possesses characteristics of both plants and animals. It contains chlorophyll similar to higher plants and thus can synthesises food in presence of light by photosynthesis.
It lacks a cell wall and also acts as heterotroph in absence of light by predating on other smaller organisms.
These are characters of animals. Thus, it is said to be a connecting link between plants and animals.