Which Statement About the Process of Muscle Contraction Is True

Which statement about the process of muscle contraction is true?

A) Calcium released into the sarcoplasm binds to tropomyosin, changing the protein's conformation.
B) When a muscle is relaxed, troponin blocks the sites on the actin filament where myosin can bind.
C) Removal of calcium from the sarcoplasm indirectly causes tropomyosin's conformation to return to the position of blocking actin-myosin binding sites.
D) Changes in tropomyosin's conformation twist troponin, exposing the actin-myosin binding sites.
E) When calcium increases in the sarcoplasm, the muscle relaxes.