Atool used in classification is
a key
a taxon
morphology
a phylum

A tool used in classification is a taxon. By definition, taxonomy is the process of systematically describing the relationship of various organisms in groups. This is used in e.g. Biology, the groupings of plants (Plantae), animals (Animalia), etc.

the answer to you question is   jet streams

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