Echo is produced due to

Options

A. reflection of sound
B. refraction of sound
C. resonance
D. none of these

Answer

### Step-by-Step Solution:

1. **Understanding Echo**:
- An echo is a sound that is reflected off a surface and heard again after a short delay.

2. **Identifying the Cause of Echo**:
- The primary reason we hear an echo is due to the reflection of sound waves. When sound waves travel and hit a surface (like a wall or a mountain), they bounce back towards the source.

3. **Analyzing the Options**:
- The question provides several options:
- A) Reflection of sound
- B) Refraction of sound
- C) Resonance
- D) None of these

4. **Evaluating Each Option**:
- **Option A (Reflection of sound)**: This is the correct answer because echo is produced when sound waves reflect off surfaces.
- **Option B (Refraction of sound)**: Refraction refers to the bending of sound waves when they pass through different mediums. This does not produce an echo.
- **Option C (Resonance)**: Resonance is the amplification of sound due to matching frequencies, but it does not directly cause an echo.
- **Option D (None of these)**: Since we have identified the correct cause, this option is incorrect.

5. **Conclusion**:
- Therefore, the correct answer is **Option A: Reflection of sound**.