Ultrasound waves propagate at 1500 m/s in water Steps:

• Identify typical sound speeds: air (330 m/s), water (1500 m/s), solids (>3000 m/s).
• Match ultrasound to medical applications in aqueous media at 1500 m/s.
• Check options: only C has 1500 m/s velocity.
• Verify wavelength (8.0 cm) yields frequency f = v/λ ≈ 18.75 kHz, near ultrasound threshold (>20 kHz).

Why C is correct:

• 1500 m/s is the speed of sound in water, the standard medium for ultrasound waves per wave propagation principles.

Why the others are wrong:

• A: 330 m/s matches air for audible sound waves.
• B: 890 m/s does not correspond to any standard medium for ultrasound.
• D: 4000 m/s is too high, typical for solids, not ultrasound in tissue/water.

Final answer: C