Solution:Concept- Sonorous refers to the ability to produce sound. All metals except mercury are found to be sonorous.
Now, metals are characterised by fewer electrons in their outermost orbital. As a result, electron bonding in metals is highly delocalized.
Therefore, when a metal surface is hit, the electron cloud in it moves easily with little energy dissipation. This allows the incoming kinetic energy to easily propagate as a wave.
Because metals have high elasticity, this wave propagates at high speed. Sound requires elasticity for high-speed propagation.
Therefore, metals are sonorous because they are highly elastic. Due to its elasticity, it can be used for high speed propagation and used for musical instruments.
Hence, the correct answer is 3.