Which best describes the process by which ultrasounds images are made?
A
Low-frequency sound waves are generated by a machine and refracted off of objects, creating echoes that are processed into images.B
High-frequency sound waves are generated by a machine and refracted off of objects, creating echoes that are processed into images.C
High-frequency sound waves are generated by a machine and reflected off of objects, creating echoes that are processed into images.D
Low-frequency sound waves are generated by a machine and reflected off of objects, creating echoes that are processed into images.