The correct answer is a diatom. Diatoms are eukaryotic single-celled organisms that functions in the ecologic population as producers as they are capable of performing photosynthesis (photoautotrophs). Mushrooms are eukaryotes but cannot perform photosynthesis. Cyanobacterium can perform photosynthesis but they are prokaryotes. E.coli cannot perform photosynthesis and they are prokaryotes as well.
