The small white insects (cochineal) that live on the beaver tail cactus in the arroyo seco suck sap and water from the cactus without providing anything for the cactus in return. this is an example of

some fungi obtain their nutrients from a living host (plant or animal) and are called most biotrophic fungi have fairly narrow host ranges—they are specialized on a limited called rhizomorphs that allow the fungus to grow from one tree to another. ascospores are formed inside a sac-like structure called an ascus. so your answer is a