What is the basic structural unit of bone?

Rationale:
A. Secretes the lubricating fluid for a synovial joint describes the synovial membrane, not a bursa.
B. Prevents friction between skin and bone, or a muscle tendon and bone; A bursa is a small, fluid-filled sac that cushions and reduces friction between moving structures, such as tendons, muscles, and bones. This helps facilitate smooth movement and prevents tissue damage.
C. Surrounds a tendon at the point where the tendon crosses a joint describes a tendon sheath, which is distinct from a bursa.
D. Is the strong band of connective tissue that holds bones together at a synovial joint refers to a ligament, not a bursa.

Rationale:
A. Lactic acid is a byproduct of anaerobic metabolism when oxygen is limited, such as during intense exercise. Muscles do not metabolize lactic acid for energy at rest.
B. Glucose is a primary fuel source during moderate to high activity, but at rest, muscles rely more on fat metabolism.
C. Creatine phosphate provides a rapid, short-term energy source during the first few seconds of intense activity, but it is not the main energy source at rest.
D. At rest, skeletal muscles primarily metabolize fatty acids through aerobic respiration to produce ATP. This is because fat provides a more efficient and long-lasting energy source during periods of low demand.