Name the anticoagulant present in blood.

Explanation

**Step-by-Step Solution:**

1. **Understanding Anticoagulants**: Anticoagulants are substances that prevent blood from clotting. This is important for maintaining proper blood circulation in the body.

2. **Identifying the Anticoagulant in Blood**: Among the various anticoagulants present in the body, we need to identify the one that is naturally occurring in blood.

3. **Naming the Anticoagulant**: The primary anticoagulant found in blood is **heparin**. Heparin is a natural substance that helps to prevent the coagulation of blood.

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