How does the sliding filament model explain muscle contraction?

• A. It describes how myosin pulls actin filaments towards the M disc, shortening the sarcomere.
• B. It explains how calcium ions bind to troponin, initiating contraction.
• C. It shows how the sarcoplasmic reticulum releases calcium.
• D. It illustrates the role of ATP in muscle relaxation.

Answer: (A)