Plasma is the fluid poion of the blood which aids in the transpo of other substances in the body. Total plasma volume in relation with body weight is:

**Core Concept**
Plasma is the liquid component of blood that facilitates the transportation of various substances throughout the body. It is a critical component of the circulatory system, comprising approximately 55% of the total blood volume.

**Why the Correct Answer is Right**
The correct answer is related to the proportion of plasma volume in relation to body weight. Plasma volume is directly proportional to body weight, with an average volume of approximately 70 mL/kg of body weight. This means that a person weighing 70 kg would have a plasma volume of approximately 4900 mL. This relationship is essential for understanding fluid balance and blood volume in clinical scenarios.

**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because it does not accurately represent the proportion of plasma volume in relation to body weight. The correct proportion is approximately 70 mL/kg, not 50 mL/kg.
* **Option B:** Incorrect because it is too low and does not accurately represent the proportion of plasma volume in relation to body weight. The correct proportion is approximately 70 mL/kg, not 30 mL/kg.
* **Option C:** Incorrect because it is too high and does not accurately represent the proportion of plasma volume in relation to body weight. The correct proportion is approximately 70 mL/kg, not 90 mL/kg.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that plasma volume is directly proportional to body weight, which is crucial for understanding fluid balance and blood volume in clinical scenarios, such as in the management of shock or during surgery.

**Correct Answer:** C.