**Core Concept**
The question is testing the student's knowledge of reactive oxygen species (ROS) and their relative reactivity. ROS are highly reactive molecules containing oxygen, which can cause cellular damage. The question requires the student to identify the strongest oxygen radical among the given options.

**Why the Correct Answer is Right**
The hydroxyl radical (OH-) is the strongest oxygen radical due to its high reactivity. It is formed through the Fenton reaction, where hydrogen peroxide (H2O2) reacts with iron ions (Fe2+). The hydroxyl radical has a very short half-life (approximately 10^-9 seconds) and reacts rapidly with cellular components, including DNA, proteins, and lipids. This reactivity makes it a potent oxidizing agent.

**Why Each Wrong Option is Incorrect**
**Option A:** Superoxide anion (O2-) is a weaker oxygen radical compared to the hydroxyl radical. Although it is still reactive, its reactivity is lower due to its lower redox potential.

**Option C:** Hydrogen peroxide (H2O2) is a relatively stable ROS and is not as reactive as the hydroxyl radical. It can be broken down by enzymes such as catalase and peroxidase to form water and oxygen.

**Option D:** Hypochlorous acid (HOCl) is a strong oxidizing agent, but it is not an oxygen radical in the same class as the hydroxyl radical. It is formed through the reaction of hydrogen peroxide with chloride ions and is used by the immune system to kill pathogens.

**Clinical Pearl / High-Yield Fact**
The hydroxyl radical is often referred to as the "most reactive oxygen species" due to its high reactivity. Understanding the relative reactivity of different ROS is crucial in understanding oxidative stress and its role in various diseases.

**Correct Answer:**
✓ Correct Answer: B. OH-