Concept:When a wave crosses a boundary between media, its frequency remains constant, while speed and wavelength change.Explanation:Sound travels faster in water than in air, so the speed increases.Frequency is determined by the source and does not change when the medium changes.Using v=fλ, if speed v increases and frequency f stays the same, then wavelength λ must also increase.Answer:B. speed and wavelength increases but its frequency remains the same