which are examples of a medium?\no water and air\no amplitude and wavelength\no crests and troughs\no…

Answer:

A. water and air

Brief Explanations:

In physics, a medium is a substance through which a wave can travel. Water and air are common media for waves like sound and water - waves. Amplitude and wavelength are wave properties, crests and troughs are parts of a wave, and compressions and rarefactions are features of sound waves in a medium, not media themselves.