Explanation

A is correct because sonography specifically uses high-frequency sound waves called ultrasonic waves. B is incorrect because electromagnetic waves include visible light and radio waves, which are different from ultrasound. C is incorrect because 'Fundamentals of waves' is a general topic, not a specific type of wave used in the procedure. D is incorrect because while some types of waves can be transverse, sonography uses mechanical sound waves that are generally longitudinal or a combination.