Answer: b. False
Step-by-step explanation: In the resting, relaxed muscle, the sarcoplasm contains a very low concentration of calcium ions. The majority of the calcium ions in a muscle cell are stored in the sarcoplasmic reticulum, which is a specialized structure within the muscle cell.
During muscle contraction, when a muscle is contracted, calcium ions are released from the sarcoplasmic reticulum into the sarcoplasm. These calcium ions then bind to specific proteins called troponin, which triggers a series of events leading to muscle contraction.
After contraction, when the muscle is relaxed, the calcium ions are actively pumped back into the sarcoplasmic reticulum, lowering the concentration of calcium ions in the sarcoplasm and allowing the muscle to return to its resting state.