THERE are natural disasters that humans can predict. There are others whose timing is difficult to know. What happened in Indonesia last month fell into the latter group. On October 25, a tsunami caused by a 7.7 magnitude earthquake in the Mentawai islands of West Sumatra, Indonesia hit shores and damaged whole villages. By last Friday, it had left about 450 dead and forced around 15,000 people to leave their homes. Tsunami is Japanese for "harbor wave". It is usually caused by a sudden rise or fall of part of the Earth's crust under the ocean. It is most common in the Pacific and Indian oceans. Normally a tsunami is a series of waves. The waves can be very long - as much as 100 kilometers - and be as far as one hour apart. They are able to cross oceans without losing much energy. When the ocean is deep, tsunamis can travel unnoticed at speeds of up to 800 kilometers an hour. They can cross a whole ocean in a day or less. The wave may only be a few meters high but when they are near the shore and reach shallow water, they build up height very quickly. Some witnesses in the Mentawai islands reported seeing up to 6-meter high waves crash onto the shore. Failed alert system Many countries set up early warning systems in their waters in the hope of giving people enough time to escape to higher ground in the event of a tsunami. But Indonesia's warning system, completed with German aid, stopped working about a month ago because of disrepair , according to the country's Meteorology and Geophysics Agency. As a result, not a single siren sounded after the earthquake. However, it was unclear if the sirens could have made a difference because the islands affected were so close to the epicenter that the tsunami would have reached them within minutes. What is the main point of the article? A) A tsunami that hit Indonesia. B) The tsunami warning system in Indonesia. C) A recent tsunami and an earthquake in Indonesia. D) The reasons why the tsunami affected Indonesia badly.
A
(Question)
Some fish may contain harmful chemicals, which can be the result of both natural causes and water pollution. Mercury is a poisonous chemical, which occurs naturally in oceans and the Earth's crust , but also comes from man-made sources, such as farm chemicals, burning garbage, oil, coal, etc. Polyclilorinated bipheuyls (PCBs), a group of chemicals, can also be found in some fish. These man-made chemicals were used in many industries until 1977, when they were banned. PCBs were released or leaked into (lie tar and water and have bear transported around the globe. How do mercury and PCBs end up in fish and the food supply? When they arc released into the air, they attach themselves to particles .These particles settle on the ground and in the water and are eventually eater by micro-organisms. Small fish cat the micro-organisms, and large fish eat the small fish and on up the food chain. Because they can negatively affect your health, the U.S. Eavirotunental Protectioc Agency advises that kids younger than 15 years old avoid fish that cortain high levels of mercury and PCBs. These include shark, swordfish, king rrnackerel, and tilefish. There are also many types of fish that are good for you, but arc in danger of being wiped out because of ovcrfishing. Sonic are being fished in the wild so much that they cannot reproduce enough to survive.Others re being farmed in ways that are not environmentally friendly. These fish include red snapper.Atlantic salmon, bluefnn tuna. and king crab. Despite these problems, there are several fish that are both healthy and sustainable , such as Alaskan salmon, American catfish, Pacific cod, and several fans-raised fish and shellfish. Which of the following is true of PCBs according to the text? A) They are transported by human beings around the globe. B) They have been widely used in &c world since 1977. C) They are hard to be cleared out from nature. D) They arc a kind of man-made fish food.
(Answer)
C
Future historians will be in a particular position when they come to record the history of our own times. They will hardly know which facts to select from the great mass of evidence that's always increasing. What is more, they will not have to rely only oh the written word. Films, videos, CDs and CD-ROMs are just some of the huge amount of information they will have. They will be able, as it were, to see and hear us in action. But the historian attempting to show the distant past again is always faced with a difficult task. He has to make proper use of evidence available to draw reasonable conclusions. Good news is that even evidence that may appear unimportant can shed light on the history of early man. Up to now, historians have assumed that calendars came into being with the appearance of agriculture, for man of that time was faced with a real need to understand something about the seasons. Recent scientific evidence seems to suggest that this assumption is incorrect Historians have long been puzzled by dots, lines and symbols which have been carved on walls, bones and so on. The nomads who made these markings lived by hunting and fishing during the last Ice Age which began about 35,000 B.C. and ended about 10,000 B.C. By comparing and analyzing markings made in various parts of the world, historians have been able to read this difficult "language". They have found that it is connected with the passing of days and the stages of the moon. It is, in fact, a primitive type of calendar. It has long been known that the hunting scenes drawn on walls were not simply a form of expression of art. They had a certain meaning, for they were as near as early man could get to writing. It is possible that there is a certain relation between these, paintings and the markings that sometimes accompany them. It seems that man was making a real effort to understand the seasons 20,000 years earlier than has been supposed. What can we infer from this passage? A) Agriculture existed thanks to calendars. B) Calendars appeared thanks to Agriculture. C) Agriculture started long before calendars appeared D) Calendars appeared long before agriculture started
D