What is the main component of mycelium in fungi?

Mycelium is primarily composed of hyphae, which are the thread-like structures that form the fungal network. These hyphae grow and spread out in soil or other substrates, enabling the fungus to absorb nutrients and water. The mycelium can be thought of as the vegetative part of the fungus, and its extensive network is crucial for the life cycle and reproductive strategies of fungi.

Spores, while important for reproduction, are not the main structural component of mycelium. Cells in fungi can include various types, but it is the hyphae that constitute the bulk of the mycelial structure. Roots are a feature of vascular plants and do not relate to the composition of fungal mycelium. Thus, the dominance of hyphae in forming mycelium makes it the correct answer.