Final answer:
The shaft of a long bone is made of compact bone, while the ends are made of spongy bone covered by compact bone. Option B correctly identifies these parts, illustrating the structure and strength of long bones.
Step-by-step explanation:
A long bone consists of a shaft composed of compact bone, and an end composed of spongy bone covered by compact bone. The correct answer to the student's question is option B: compact bone, spongy bone covered by compact bone.
The shaft, known as the diaphysis, is formed of compact bone to provide strength and resistance to bending. The ends of the bone, referred to as the epiphysis, contain spongy bone, which has an open, lattice-like structure made of tiny plates called trabeculae. These structures help the bone to sustain lighter, multi-directional forces and also contain red bone marrow, important for blood cell production.
Furthermore, the outer boundary of the bone is comprised of compact bone tissue, which is dense and strengthens the structure. This compact bone encases the spongy bone within the epiphysis, providing an additional layer of protection and support.