*Question*
Answer the following question given this paragraph: Ultrasound in Medical Diagnostics When used for imaging, ultrasonic waves are emitted from a transducer, a crystal exhibiting the piezoelectric effect (the expansion and contraction of a substance when a voltage is applied across it, causing a vibration of the crystal). These highfrequency vibrations are transmitted into any tissue in contact with the transducer. Similarly, if a pressure is applied to the crystal (in the form of a wave reflected off tissue layers), a voltage is produced which can be recorded. The crystal therefore acts as both a transmitter and a receiver of sound. Ultrasound is also partially absorbed by tissue on its path, both on its journey away from the transducer and on its return journey. From the time between when the original signal is sent and when the reflections from various boundaries between media are received, (as well as a measure of the intensity loss of the signal), the nature and position of each boundary between tissues and organs may be deduced. Reflections at boundaries between two different media occur because of differences in a characteristic known as the acoustic impedance Z of each substance. Impedance is defined as. Q: What diagnostic technology uses high-frequency vibrations transmitted into any tissue in contact with the transducer? Choices: - laser - radiation - sonar - ultrasound A:
**Answer**
ultrasound

*Question*
Answer the following question given this paragraph: The pupil is an opening in the front of the eye. It looks black because it doesn't reflect any light. All the light passes through it instead. The pupil controls the amount of light that enters the eye. It automatically gets bigger or smaller to let more or less light in as needed. Q: What is the opening in the front of the eye called? Choices: - lens - cornea - iris - pupil A:
**Answer**
pupil

*Question*
Answer the following question given this paragraph: Mammals breathe with the help of a diaphragm. This is the large muscle that extends across the bottom of the chest below the lungs. When the diaphragm contracts, it increases the volume of the chest. This decreases pressure on the lungs and allows air to flow in. When the diaphragm relaxes, it decreases the volume of the chest. This increases pressure on the lungs and forces air out. Q: What muscle in the chest helps inflate and deflate the lungs? Choices: - pectoral - cartilage - heart - diaphragm A:
**Answer**
diaphragm

*Question*
Answer the following question given this paragraph: Advection fog is famous in San Francisco, California. Warm, moist air comes in from the Pacific Ocean. The air blows over the cold California current. When the air cools below its dew point, fog forms. Sea breezes bring the fog onshore. Q: What forms after air cools below its dew point? Choices: - sleet - smoke - plasma - fog A:
**Answer**
fog