The organism shown is a free-living one that is anchored to the bottom of ponds and streams during one stage of its life cycle. What is the common name of the group to which this organism belongs? bryozoans rotifers cnidarians mollusks there is a picture in the file below.

cnidarians

Explanation:

bryozoan - "Bryozoa are a phylum of aquatic invertebrate animals. Typically about 0.5 millimetres long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia." -Wikipedia

rotifers - "The rotifers, commonly called wheel animals or wheel animalcules, make up a phylum of microscopic and near-microscopic pseudocoelomate animals." -Wikipedia

cnidarians - "Cnidaria is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments: they are predominantly marine. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick.

" -Wikipedia

mollusks - "Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks. Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species. The proportion of undescribed species is very high." -Wikipedia

(The Wikipedia entries are for describing.)

If you look at the pictures of all the answers, cnidarians look the most like the organism in the picture shown.

69 is the correct math for the amino acids