Euglena, a unicellular freshwater protist, is shown above. Which pair of
lettered organelles likely originated from photosynthetic and aerobic
bacteria?
A)1 and 2
B)3 and 8
C) 5 and 4
D) 7 and 11

Option B is likely originated from photosynthetic bacteria.

Explanation:

A) pellicle and contractile vacoule

B) Stigma and chloroplast (photosynthetic bacteria)

C) reservoir and  flagellum

D) photoreceptor and Nucleolus

Euglena is a genus of single cell flagellate eukaryotes. Euglena have features of both animals and plants. Euglena have photosynthesizing chloroplasts within the body of the cell, which enable them to feed by autotrophy, like plants. Euglena's chloroplasts evolved from a eukaryotic green alga. Thus, the intriguing similarities between Euglena and the plants have arisen of a secondary endosymbiosis. Molecular phylogenetic analysis support this hypothesis but this is not generally accepted. A stigma (red eyespot) is located near the base of the reservoir and this filters the light and focuses it on the paraflagellar body, and is involved in the phototaxis of this alga.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."