**Core Concept**
The second injury in an explosion is a phenomenon where the initial blast wave causes a secondary injury due to the displacement and movement of objects, people, and debris. This is a result of the blast wave's pressure wave interacting with the surrounding environment, causing objects to be thrown or people to be knocked over.

**Why the Correct Answer is Right**
The correct answer is related to the concept of "blast loading" and the way it affects the human body and the surrounding environment. When an explosion occurs, a high-pressure blast wave is generated, which can cause damage to structures and people. The second injury is often caused by the displacement of objects, such as flying debris or falling objects, which can strike people and cause additional injuries. This is why the correct answer is related to the movement of objects and debris.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specifically address the concept of second injury in an explosion. While it may be related to the topic, it is not the correct answer.
**Option B:** This option is incorrect because it does not accurately describe the second injury in an explosion. The correct answer is related to the movement of objects and debris, not the initial blast wave itself.
**Option C:** This option is incorrect because it is not directly related to the second injury in an explosion. While it may be a related concept, it is not the correct answer.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the second injury in an explosion is often caused by the movement of objects and debris, rather than the initial blast wave itself. This is why it is crucial to assess the scene of an explosion carefully and look for potential hazards, such as falling objects or flying debris.

**Correct Answer: D. Secondary blast injury due to displacement of objects and debris.**