Now listen to part of a lecture in a general science class. The professor is discussing the way that ultrasound works. Ques

Narrator 2: Number 6. Listen to part of a lecture. Then listen for a question about it. After you hear the question, you have 20 seconds to prepare and 60 seconds to record your answer.
Narrator 1: Now listen to part of a lecture in a general science class. The professor is discussing the way that ultrasound works.
Professor:
Okay, let’s talk about how ultrasound works, and how it’s used in medical diagnosis. To make a long story short, ultrasound is very similar to the sonar devices we discussed last week. Remember the system that emits ultrasonic pulses and listens for reflected pulses from objects in the ocean? Well, ultrasound is really just another type of sonar. The sound waves used in the ultrasound are created by a crystal that moves rapidly back and forth, creating a sound, but you can’t hear it because the frequency is so high. The doctor places the device, the transmitter that sends out the sound waves...the doctor puts that on the surface of the skin so the sound waves are transmitted inside the body. And when this high-frequency sound is directed to a particular area, then the tissue and organs reflect the sound. The patterns of sound that are reflected are processed by a computer, and an image appears on the screen.
And that tells the doctor whether there is something unusual there or not. This is very important in the diagnosis of cancer...to know whether a tumor is present...and also as a noninvasive way to
monitor the growth of a fetus during pregnancy.
Narrator 1: Using the main points and examples from the lecture, describe the kind of information that ultrasound can provide, and then explain the way that ultrasound is used in medical diagnosis.
Narrator 2: Please prepare your answer after the beep.
Beep
[Preparation time: 20 seconds]
Narrator 2: Please begin speaking after the beep.
Beep
[Recording time: 60 seconds]
Beep