**Core Concept**
The management of significant blood volume loss, such as 40% loss, involves understanding the principles of **hypovolemic shock** and the body's compensatory mechanisms, including the role of the **sympathetic nervous system** and the **renin-angiotensin-aldosterone system**.

**Why the Correct Answer is Right**
In the case of a 40% loss of blood volume, the patient is likely to be in severe hypovolemic shock, characterized by decreased **cardiac output**, **peripheral resistance**, and **blood pressure**. Management involves aggressive fluid resuscitation to restore blood volume, often with **crystalloids** or **colloids**, and may require **vasopressors** to support blood pressure.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect as it may not provide adequate volume expansion.
**Option B:** Incorrect as it is not the primary management for hypovolemic shock.
**Option C:** Incorrect because, although it may be used, the question asks for the management of a 40% loss, which typically requires more than just monitoring.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the management of hypovolemic shock due to significant blood loss involves not just fluid resuscitation but also identifying and addressing the underlying cause of the blood loss.

**Correct Answer: D.** Fluid resuscitation and blood transfusion as needed.