Match the role of ATP and Calcium in muscle contraction.
| Column I | Column II |
|---|---|
| (a) ATP binding | (i) Binds with troponin to unmask active sites |
| (b) ATP hydrolysis | (ii) Causes the detachment of myosin from actin |
| (c) Calcium ions (Ca²⁺) | (iii) Provides energy for the power stroke |
| (d) Sarcoplasmic reticulum | (iv) Stores and releases calcium ions |