Answer the following question given this paragraph: Did you ever hear an echo of your own voice? An echo occurs when sound waves bounce back from a surface that they can't pass through. The woman pictured here is trying to create an echo by shouting toward a large building. When the sound waves strike the wall of the building, most of them bounce back toward the woman, and she hears an echo of her voice. An echo is just one example of how waves interact with matter. Q: What is heard when sound waves bounce back from a surface that they can't pass through? Choices: - radio - ultrasound - loop - echo A:
echo

Answer the following question given this paragraph: Fixed joints do not allow any bone movement. Many of the joints in your skull are fixed ( Figure below ). There are eight bones that fuse together to form the cranium. The joints between these bones do not allow movement, which helps protect the brain. Q: How many bones fuse together to form the cranium? Choices: - 6 - 3 - 8 - 8 A:
8

Answer the following question given this paragraph: Unlike bones and tendons, which need to be strong as well as elastic, the arteries and lungs need to be very stretchable. The elastic properties of the arteries are essential for blood flow. The pressure in the arteries increases and arterial walls stretch when the blood is pumped out of the heart. When the aortic valve shuts, the pressure in the arteries drops and the arterial walls relax to maintain the blood flow. When you feel your pulse, you are feeling exactly thisthe elastic behavior of the arteries as the blood gushes through with each pump of the heart. If the arteries were rigid, you would not feel a pulse. The heart is also an organ with special elastic properties. The lungs expand with muscular effort when we breathe in but relax freely and elastically when we breathe out. Our skins are particularly elastic, especially for the young. A young person can go from 100 kg to 60 kg with no visible sag in their skins. The elasticity of all organs reduces with age. Gradual physiological aging through reduction in elasticity starts in the early 20s. Q: What causes reduction of elasticity in all organs? Choices: - low vitamin D - radiation - weight gain - age A:
age