……………… ions play a significant role in blood clotting .

Explanation

**Step-by-Step Solution:**

1. **Understanding Blood Clotting**: Blood clotting, also known as coagulation, is a crucial physiological process that prevents excessive bleeding when there is an injury to blood vessels.

2. **Role of Platelets**: Platelets, a type of blood cell, play a significant role in the formation of clots. When there is an injury, platelets aggregate at the site and initiate the clotting process.

3. **Importance of Ions in Clotting**: Various ions are involved in the blood clotting process, but one ion stands out for its significant role.

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