In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

Which of the following is not a dinophyte: Kryptoperidinium, ribosomes, or Durinskia?, Context: Some dinophytes, like Kryptoperidinium and Durinskia have a diatom (heterokontophyte) derived chloroplast. These chloroplasts are bounded by up to five membranes, (depending on whether you count the entire diatom endosymbiont as the chloroplast, or just the red algal derived chloroplast inside it). The diatom endosymbiont has been reduced relatively littleit still retains its original mitochondria, and has endoplasmic reticulum, ribosomes, a nucleus, and of course, red algal derived chloroplastspractically a complete cell, all inside the host's endoplasmic reticulum lumen. However the diatom endosymbiont can't store its own foodits starch is found in granules in the dinophyte host's cytoplasm instead. The diatom endosymbiont's nucleus is present, but it probably can't be called a nucleomorph because it shows no sign of genome reduction, and might have even been expanded. Diatoms have been engulfed by dinoflagellates at least three times.
ribosomes