Answer: Decreased bone density making bones fragile and prone to fracture.
- A A bacterial infection that spreads through the bone marrow cavity over time
- B Decreased bone density making bones fragile and prone to fracture
- C Excessive new bone growth causing abnormal thickening of the skeleton
- D Inflammation of the synovial joints and surrounding cartilage tissue
Correct answer: B. Decreased bone density making bones fragile and prone to fracture
Explanation: Osteoporosis is a condition where bone mineral density decreases, making bones brittle and prone to fracture. It is most common in post-menopausal women (estrogen loss) and older adults. Prevention: calcium, vitamin D, weight-bearing exercise.
A sarcomere (Z line to Z line): during contraction the I band and H zone shorten as thin filaments slide over thick, while the A band stays the same length. Image: SlothMcCarty, CC BY-SA 3.0, via Wikimedia Commons.
Concept context
Types of movement, muscle contraction, skeletal system, joints, and disorders. Important for Class 11 and NEET.