Serum is

Options

A. blood minus fibrinogen
B. lymph minus corpuscles
C. lymph
D. blood minus corpuscles and fibrinogen

Explanation

**Step-by-Step Solution:**

1. **Definition of Serum**: Serum is defined as the fluid component of blood that remains after the blood has clotted. It is essentially the liquid part of the blood without the cells and clotting factors.

2. **Components of Blood**: Blood consists of various components, primarily:
- Red Blood Cells (RBCs)
- White Blood Cells (WBCs)
- Platelets
- Plasma (the liquid component that contains water, electrolytes, proteins, hormones, and waste products)

3. **Understanding Plasma and Serum**:
- Plasma is the liquid portion of blood that contains clotting factors, which are essential for the blood coagulation process.
- Serum is obtained by removing the clotting factors from plasma. Therefore, serum does not contain RBCs, WBCs, platelets, or clotting factors.

4. **Clotting Factors**: The major clotting factor in blood is fibrinogen. Fibrinogen is a soluble protein that, when activated, converts to fibrin, forming a mesh that helps in blood clotting.

5. **Conclusion**: Therefore, serum can be described as blood minus the cellular components (RBCs, WBCs, and platelets) and minus the clotting factors (including fibrinogen).

6. **Final Answer**: Serum is blood minus corpuscles (RBCs and WBCs) and fibrinogen (the major clotting factor).

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