Answer: Twelve.
- A Twelve
- B Ten
- C Eight
- D Twenty
Correct answer: A. Twelve
Explanation: Humans have 12 pairs of ribs attached to the thoracic vertebrae.
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.