About 1.5 million species of fungi exist on Earth. They act as nature’s decomposers, breaking down matter, releasing enzymes and acids that unlock nutrients for plants and soil organisms. You may be familiar with macro-fungi, a type of fungus that includes mushrooms. But for the most part, fungi exist as mycelia, tiny threads that snake underground in billions of interconnected threads. They twist and twine with tree root systems, bringing them crucial nutrients. Mycologists call these networks of mycelia "Earth’s nervous system." Which statement best identifies the central idea of the paragraph? A. The over a million different types of fungi surrounding us act as Earth's decomposers. B. The type of fungus called macrofungi includes mushrooms. C. Fungi exist as a web of threads connected underground. D. Fungi bring nutrients to tree root systems when they twine with them underground.