**Core Concept**
The underlying principle being tested is the **cold pressor test**, which assesses the integrity of the **sympathetic nervous system**. This test is used to evaluate **vasomotor reflexes** and **autonomic function**.

**Why the Correct Answer is Right**
The correct answer choice is related to the most effective method for performing the cold pressor test. Since the actual options are missing, let's assume the correct answer involves applying cold to a specific area of the body. The mechanism involves the stimulation of **cold receptors**, leading to a reflexive increase in **sympathetic outflow**, which then causes **vasoconstriction** and an increase in **blood pressure**.

**Why Each Wrong Option is Incorrect**
**Option A:** Might be incorrect if it involves an inappropriate method or area for cold application.
**Option B:** Could be wrong if it suggests an ineffective or unsafe way to apply cold.
**Option C:** May be incorrect if it proposes a method that does not adequately stimulate the desired reflex.

**Clinical Pearl / High-Yield Fact**
The cold pressor test is a simple, non-invasive method to assess the **autonomic nervous system**. Remember, the test should be performed with caution in patients with certain cardiovascular conditions.

**Correct Answer:** D. By immersion of the hand in ice-cold water.