Final answer:
The extracellular matrix is mainly composed of collagen fibers, ground substance, as well as other components like elastin fibers and proteoglycans, which together provide structural support and help in cellular communication.
Step-by-step explanation:
The extracellular matrix is composed of various components, crucial for providing structural support to cells and facilitating communication between them. Among the options given, collagen fibers and ground substances are indeed part of the extracellular matrix. Collagen is the most abundant protein in the matrix, giving it strength and structure, and ground substance is a viscous, colorless fluid that fills the space between cells and fibers, often composed of proteoglycans and hyaluronic acid. Although not listed in the options, other key components include elastin fibers, which provide elasticity, and proteoglycans, which contribute to the matrix's bulk.