Question

this group formally lacks true tissues but does have several differentiated cell types.
a mollusca
b cnidaria
c porifera
d annelida
e platyhelminthes

Explanation:

• Mollusca: Have true tissues and complex organ systems.
• Cnidaria: Have true tissues (e.g., epidermis, gastrodermis).
• Porifera (sponges): Lack true tissues but have different cell types like choanocytes, pinacocytes.
• Annelida: Have true tissues and segmented body plans with complex organ systems.
• Platyhelminthes: Have true tissues (e.g., they have three germ - layers and organ - level organization).

Answer:

C. Porifera