Why is a matching layer typically composed of multiple layers, and how do the material properties contribute to overall performance?

• A. Multiple layers create gradual impedance steps between PZT and tissue, reducing reflections across a broad frequency range and expanding bandwidth for better energy transfer.
• B. Multiple layers amplify reflections for better imaging.
• C. Using a single layer would better expand bandwidth.
• D. Layers are only for cosmetic purposes.

Answer: (A)