Considering that millions of species have lived on earth why are there relatively few fossils

They might not have been well-preserved, making them rot faster and seemingly not exist.

Explanation:

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