A sponge and a cnidarian are compared in class. The sponge differs most clearly because it has cellular-level organization and choanocyte-based filter feeding. In an exam answer, the key reason is: (276)

Correct Answer: B

cellular-level organization with choanocytes

Sponges lack true tissues and use choanocytes for water currents and feeding. Cnidarians have tissue-level organization and cnidocytes, so these characters separate the two early animal phyla. This question is designed as a comparison-based item to reduce thin-content style repetition and improve conceptual depth.