**Core Concept**
The patient's body will undergo a series of physiological responses to compensate for the massive blood loss, including changes in cardiac output, peripheral resistance, and fluid shifts. The body's ability to maintain homeostasis is crucial in this scenario.

**Why the Correct Answer is Right**
In a normotensive patient with normal hemoglobin who suffers massive blood loss, the body's compensatory mechanisms will lead to an increase in cardiac output and peripheral vasoconstriction to maintain blood pressure. This is mediated by the sympathetic nervous system, which releases catecholamines such as epinephrine and norepinephrine. The increase in cardiac output is achieved through an increase in heart rate and contractility, while peripheral vasoconstriction reduces blood flow to non-essential areas and directs it to vital organs.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because massive blood loss will not lead to an increase in hematocrit (the proportion of blood volume occupied by red blood cells). In fact, the hematocrit will decrease due to the loss of blood volume.
* **Option B:** This option is incorrect because tachycardia (rapid heart rate) is a common response to massive blood loss, as the body attempts to compensate for the decreased blood volume by increasing cardiac output.
* **Option C:** This option is incorrect because peripheral vasoconstriction is a normal response to massive blood loss, as the body attempts to direct blood flow to vital organs and reduce blood flow to non-essential areas.

**Clinical Pearl / High-Yield Fact**
In a patient with massive blood loss, the body's ability to maintain homeostasis is crucial, and the compensatory mechanisms can be remembered by the mnemonic "CAB" - Cardiac output increases, Blood pressure is maintained, and Adrenaline is released.

**Correct Answer: A. Decrease in hematocrit**