You will be given a definition of a task first, then some input of the task.
In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

suggests that one organism in this phylum introduced the parasite Haplosporidium nelsoni to the Chesapeake Bay. That organism is Crassostrea gigas. The laterofrontal cirri of the ctenidia in this phylum filter and retain particles. Some organisms in this phylum use byssal threads to attach themselves to a substrate. Filter feeders in this phylum excrete pseudofeces and notably lack a toothed chitinous ribbon. Important features of this phylum include an extension of the body wall which is often responsible for secreting a calcium carbonate shell, the mantle, as well as the radula. For 10 points, name this phylum containing the classes Gastropoda and Bivalvia, examples of which are snails and mussels.
Output:
Science