40 POINTS! please help!

Medical imaging can be accomplished with ultrasound technology, which uses high-frequency sound waves. A technician passes a wand-like device across the patient's skin. The device both transmits and receives sound waves.
Which statement best explains why sound waves are useful for medical imaging?
A: Sound waves are either absorbed by internal organs or transmitted through them.
B: Many internal organs generate sound waves, which can be detected on the surface.
C: All body tissues reflect or transmit sound waves in the same way.
D: Various body tissues differ in their reflection and transmission of sound waves.