Answer
c. animals
Work Step by Step
Choanoflagellates are protists that are the most related to animals. Most of these protists live individually as single cells, but some exist as colonies of cells in which the daughter cells do not separate completely after mitosis. Adhesion proteins keep the cells together; these proteins are similar to adhesion proteins in animals.
Scientists hypothesize that, originally, an ancestor protist used adhesion proteins to capture prey; these proteins eventually helped the choanoflagellates stick together in colonies. Over time, this protist gave rise to multicellular animals formed from single-celled animal cells that stuck together using these adhesion proteins.
