【正文】 fe cycle.First of all, the starfish are not really fish. They belong to the family of echinoderms which are spinyskinned sea animals. That is their skin is covered with thorny bumps. Most starfish have five armliked extensions on their bodies, and so they look like a fivepointed star. But some other kinds have as many as 40 or more arms. Starfish like other members of the echinoderm family have what’s called radio symmetry. All that means is that the body parts of these animals are arranged around the center, kind of like spokes of a wheal around the hub.One of the special features of the starfish is that it can drop off arms as a defensive reaction, to get away from an attacker, for example. They can then grow new arms to replace the old ones.Starfish reproduce by releasing eggs into the sea. These eggs develop into larvae and can swim freely. These early forms which the larvae are differ from adult starfish because the larvae have bilateral symmetry. That means that the two halves of the larvae look exactly the same, which makes them look a lot different from the later form of the star fish. Eventually, the larvae sink to the ocean bottom and charge into the adult radio form. If you don’t have any question, we’ll go in now and see some of these creatures in person.43. What is the talk mainly about?(A) Reproduction in echinoderms.(B) How fish avoid their enemies.(C) The form and life cycle of starfish.(D) The feeding habits and digestive（消化的） systems of ：C44. What does the speaker say about the skin of echinoderms?(A) It consists of a protective film.(B) It is covered with scales.(C) It can be shed （脫落）easily.(D) It is covered with sharp ：D45. Why does the speaker give the example of the hub of a wheel surrounded by spokes?(A) To explain how a starfish reproduces.(B) To illustrate the shape of a starfish.(C) To demonstrate the defense mechanisms of starfish.(D) To show how larvae change into adult ：B46. What happens if a starfish loses an arm?(A) It generates a new one.(B) It cannot swim.(C) It is easily caught.(D) It dies soon ：A47. What is the major difference between newly developed and adult starfish?(A) Their diet.(B) The shape of their bodies.(C) Where they feed.(D) Their method of ：BQuestions 4850 Listen to part of a talk in the United States history class. The professoris discussing the Civil War.Last time, we outlined how the Civil War finally got started. I want to talk today about the political management of the war on both sides: the north under Abraham Lincoln and the south under Jefferson Davis. An important task for both of these presidents was to justify for their citizens just why the war was necessary.In 1861, on July 4th, Lincoln gave his first major speech in which he presented the northern reasons for the war. It was, he said, to preserve democracy. Lincoln suggested that this war was a noble crusade that would determine the future of democracy through out the world. For him the issue was whether or not this government of the people, by the people could maintain its integrity, could it remain plete and survive its domestic foes. In other words, could a few discontented individuals and by that he meant those who led the southern rebellion, could they arbitrarily break up the government and put an end to free government on earth? The only way for the nation to survive was to crush the rebellion.At the time, he was hopeful that the war wouldn’t last long and the slave owners would be put down forever, but he underestimated how difficult the war would be. It would be harder than any the Americans had thought before or since, largely because the north had to break the will of the southern people, not just by its army. But Lincoln rallied northerners to a deep mitment to the cause. They came to perceive the war as a kind of democratic crusade against southern society.48. What is the talk mainly about?(A) Advantages of the North in the Civil War.(B) Civilian（平民） opposition （反對(duì)）to the Civil War.(C) Reasons to justify fighting the Civil War.(D) Military strategy used in the Civil ：C49. What does the speaker imply was the purpose of Lincoln’s speech?(A) To suggest changes to government structure.(B) To criticize the practice（n實(shí)行） of slavery（奴隸制度）.(C) To convince（說(shuō)服） the South to surrender（投降）.(D) To inspire（鼓舞） Northerners to support the ：D50. Who were the discontented individuals to whom Lincoln referred in his speech?(A) Leaders of the Southern rebellion.(B) Slaves in the Southern states.(C) Northern opponents of the war.(D) Southern soldiers.