[填空题]The causes for the stagnation are ______.

[单项选择] Earthquakes What causes earthquakes The earth is formed of layers. The surface of the earth, about 100 kilometers thick, is made of large pieces. When they move against each other, an earth quake happens, A large movement causes a violent earthquake, but a small movement causes a mild one. Earthquakes last only a few seconds. The rolling movements are called seismic (地震的) waves. The seismic waves start in one place, called the epicenter (震中) , and roll outward. A seismic wave travels around the earth in about twenty minutes. Usually, an earthquake is strong enough to cause damage only near its epicenter. However, epicenters at the bottom of the ocean create huge sea waves as tall as 15 meters. These waves cross the ocean in several hours. Rushing toward land, they destroy small islands and ships in their path. When they hit land, they flood coastal areas far from the epicenter of the earthquake. In 1868, a wave reached 4. 5 kilometers inland in P
A. Y
B. N
C. NG

[填空题]Carbon monoxide poisoning causes death and injuries throughout the world. The poison gas has been a problem since humans first began burning (36) to cook food or to create heat during cold weather. More people die from carbon monoxide poisoning in the United States each year than from any other kind of poisoning. Carbon monoxide gas is called the such a silent (37) that it is hard for people to (38) it in the air. Yet, carbon monoxide gas is very (39) It steals the body’s ability to use oxygen. Carbon monoxide (40) the ability of the blood to carry oxygen to body tissues. It does this by (41) with the blood. When carbon monoxide links with the blood, the blood is no longer able to carry oxygen to the tissues that need it. (42) to the body can begin very quickly from large (43) of this gas. (44) and the amount of the gas he or she breathes in. Small amounts of carbon monoxide will cause a