The correct option is B Ultrasonography
A sound which has a frequency of 20,000 Hz or more, is called ultrasonic sound, or simply, ultrasound.
Ultrasonic sound waves are made to reflect from various parts of the heart, and form an image of the heart. This technique is called echocardiography.
Images of body organs are generated by sending ultrasonic sound through the tissues of human body. This is called ultrasonography.
MRI uses magnetic fields and radio waves to capture images of the organs.
Loudspeakers are devices that increases the amplitude of sound waves with the help of electrical energy.