Given a scientific passage and an answer, generate a question for the given answer.

Passage: Although lots of symbiotic relationships help both organisms, sometimes one of the organisms is harmed. When that happens, the organism that benefits, and is not harmed, is called a parasite . This type of relationship is known as parasitism. Answer: parasite
Although lots of symbiotic relationships help both organisms, sometimes one of the organisms is harmed. when that happens, the organism that benefits, and is not harmed, is called a what?

Passage: Most plant cells have a large central vacuole . It can make up as much as 90 percent of a plant cell's total volume. The central vacuole is like a large storage container. It may store substances such as water, enzymes, and salts. It may have other roles as well. For example, the central vacuole helps stems and leaves hold their shape. It may also contain pigments that give flowers their colors. Answer: vacuole
Most plant cells have a large central what?

Passage: Sperm are released into the surrounding water through the osculum. If they enter a female sponge through a pore, they may be trapped by collar cells. Trapped sperm are delivered to eggs inside the female body, where fertilization takes place. The resulting zygote develops into a larva. Unlike the adult, the larva is motile. It is covered with cilia that propel it through the water. As the larva grows, it becomes more similar to an adult sponge and loses its ability to swim. Answer: larva
Unlike an adult sponge, what stage is motile due to cilia that propel it through water?