**Core Concept**
Phase 1 clinical trials are the first stage of testing in human subjects, primarily involving the administration of a new drug or treatment to a small group of normal human volunteers to assess its safety, tolerability, pharmacokinetics, and pharmacodynamics.

**Why the Correct Answer is Right**
The primary goal of Phase 1 clinical trials is to evaluate the safety and tolerability of a new intervention in a small group of healthy volunteers. This phase assesses the maximum tolerated dose, pharmacokinetic profiles, and potential side effects. The participants are typically healthy individuals who do not have any underlying medical conditions that could affect the trial outcomes.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Phase 2 clinical trials involve a larger group of patients, often with the disease or condition the new intervention is intended to treat.
**Option B:** This option is incorrect because Phase 3 clinical trials are conducted in a larger population and are primarily designed to evaluate the efficacy of the new intervention compared to existing treatments.
**Option C:** This option is incorrect because Phase 4 clinical trials, also known as post-marketing surveillance trials, are conducted after the new intervention has been approved and marketed to gather more information on its long-term safety and efficacy.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Phase 1 clinical trials are crucial for establishing the safety profile of a new intervention and are often conducted in healthy volunteers to minimize the risk of adverse events.

**Correct Answer:** A.