Context: Protist is an informal term for any eukaryotic organism that is not an animal, plant or fungus. The protists do not form a natural group, or clade, but are often grouped together for convenience, like algae or invertebrates. In some systems of biological classification, such as the popular 5-kingdom scheme proposed by Robert Whittaker in 1969, the protists make up a kingdom called Protista, composed of "organisms which are unicellular or unicellular-colonial and which form no tissues.", The metamonads are a large group of flagellate amitochondriate protozoa . Their composition is not entirely settled , but they include the retortamonads , diplomonads , and possibly the parabasalids and oxymonads as well . These four groups are all anaerobic , occurring mostly as symbiotes of animals ., A flagellate is a cell or organism with one or more whip-like organelles called flagella. The word "flagellate" also describes a particular construction (or level of organization) characteristic of many protists (eukaryotic organisms) and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagellae. However, the term "flagellate" is included in other terms (such as "dinoflagellate" and "choanoflagellata") which are more formally characterized., The retortamonads are a small group of flagellates, most commonly found in the intestines of animals as commensals, although a free-living species called the "Chilomastix cuspidata" exists. They are grouped under the taxon, Archezoa. They are usually around 5-20 m in length, and all of their small subunit ribosomal RNA gene sequences are very similar to each other. There are two genera: "Retortamonas" with two flagella, and "Chilomastix" with four. In both cases there are four basal bodies anterior to a prominent feeding groove, and one flagellum is directed back through the cell, emerging from the groove., The dinoflagellates (Greek  "dinos" "whirling" and Latin "flagellum" "whip, scourge") are a large group of flagellate protists that constitute the phylum Dinoflagellata. Most are marine plankton, but they are common in freshwater habitats, as well. Their populations are distributed depending on temperature, salinity, or depth. Many dinoflagellates are known to be photosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey (phagotrophy). In terms of number of species, dinoflagellates form one of the largest groups of marine eukaryotes, although this group is substantially smaller than the diatoms. Some species are endosymbionts of marine animals and play an important part in the biology of coral reefs. Other dinoflagellates are unpigmented predators on other protozoa, and a few forms are parasitic (see for example "Oodinium", "Pfiesteria"). Some dinoflagellates produce resting stages, called dinoflagellate cysts or dinocysts, as part of their lifecycles., Subject: metamonad, Relation: instance_of, Options: (A) animal (B) biology (C) cell (D) clade (E) classification (F) construction (G) dinos (H) group (I) organism (J) organization (K) plant (L) taxon (M) term (N) whip
Output: taxon