Sponges are made up of how many layers of cells? What structures on the body of the sponge allow water to enter?

Here are the solutions to the questions:

11. Sponges are made up of D. two layers of cells. Sponges are simple multicellular organisms that lack true tissues and organs. Their body wall is generally composed of two main layers of cells (pinacoderm and choanoderm) separated by a gelatinous mesohyl.

12. What structures on the body of the s_____ (The question is cut off, but assuming it refers to sponges based on the previous question and options) C. pores. Sponges are characterized by their porous bodies. Water enters through numerous small pores called ostia and exits through a larger opening called the osculum. They do not possess a backbone or a brain.

The final answer for 11 is $\boxed{\text{D}}$
The final answer for 12 is $\boxed{\text{C}}$