The correct option is B Chlamydomonas
Chlamydomonas is an eukaryotic, unicellular algae. It has chloroplasts and performs photosynthesis; hence, autotrophic. It usually lives in an aquatic medium.
Entamoeba histolytica is also an aquatic eukaryotic organism but lacks chlorophyll.
Salmonella typhi and Treponema pallidum are bacteria. All bacteria are prokaryotes.