Approximately how much sound energy can be lost at the skin's surface due to trapped air, and what property accounts for this loss?
A) 5-10%, due to acoustic impedance mismatch
B) 20-30%, due to high thermal conductivity
C) 40-50%, due to low viscosity of the coupling medium
D) 60-70%, due to high absorption coefficient
E) 80-90%, due to increased frequency of the ultrasound waves