The speed of sound is fastest in -

Correct option is A

The correct answer is (a) Steel

The speed of sound generally increases as the density and elasticity of the medium increase.
In solids, particles are closely packed, which allows sound waves to travel faster.
Steel (a solid) has a much higher speed of sound (~5,960 m/s) compared to water (~1,500 m/s), air (~343 m/s), or milk (similar to water).

Additional Information:

• Air: ~343 m/s (at 20°C)
• Water: ~1,500 m/s
• Steel: ~5,960 m/s (varies with type of steel)

Sound travels fastest in solids, slower in liquids, and slowest in gases due to the differences in particle spacing and elasticity of the medium.