Which of the following statements is true?

Options

A. Sound travels faster in iron than in water.
B. Sound can travel through inert gases
C. Sound travels in the form of compressions and rarefactions in air.
D. All the above

Explanation

To determine which of the statements about sound is true, let's analyze each statement step by step.

### Step 1: Analyze the First Statement
**Statement 1:** Sound travels faster in iron than in water.

- **Explanation:** Sound travels fastest in solids, followed by liquids, and then gases. Iron is a solid, and water is a liquid. Since the particles in solids are closely packed, sound waves can travel through them more quickly due to the efficient transfer of vibrations. Therefore, this statement is **true**.

### Step 2: Analyze the Second Statement
**Statement 2:** Sound can travel through inert gases.

- **Explanation:** Inert gases, such as helium and argon, do not participate in chemical reactions under normal conditions, but they can still transmit sound. Sound is a mechanical wave that requires a medium (solid, liquid, or gas) to propagate. Inert gases can carry sound waves because they consist of particles that can vibrate and transmit sound. Hence, this statement is also **true**.

### Step 3: Analyze the Third Statement
**Statement 3:** Sound travels in the form of compressions and rarefactions in air.

- **Explanation:** Sound waves in air are longitudinal waves that consist of alternating regions of compressions (where particles are close together) and rarefactions (where particles are spread apart). This is the fundamental nature of how sound propagates in a medium like air. Therefore, this statement is **true**.

### Step 4: Conclusion
Since all three statements are true, we can conclude that the correct answer is:

**Option 4: All of the above.**

### Summary of Steps:
1. **Check the first statement:** Sound travels faster in solids than in liquids. (True)
2. **Check the second statement:** Sound can travel through inert gases. (True)
3. **Check the third statement:** Sound travels in compressions and rarefactions in air. (True)
4. **Final conclusion:** All statements are correct, so the answer is option 4.