【托福写作机经】2025年3月22日托福考试回忆

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　　 主题：药物测试（drug testing）是否有必要

　　药物测试成本过高（high cost）。

　　如果未经充分测试的药物上市，一旦出现严重不良反应，可能会对大量患者的生命健康造成威胁。

　　测试结果存在不确定性（uncertainty of results）。

　2. 虽然临床试验环境与真实世界有差异，但药物测试是目前评估药物安全性和有效性最有效的手段（the most effective means）。

　　3.测试过程耗时过长（time - consuming process）。

　测试过程耗时是为了充分保障患者安全（ensure patient safety）。快速上市未经充分测试的药物，可能让患者成为 “小白鼠”，承受不可预测的后果。

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主题：维京人离开格陵兰岛的原因

　First, climate change might have made farming in the colony impossible, exposing the Vikings to starvation. In the tenth century, the North Atlantic was somewhat warmer than it is today; this, historians believe, is what allowed the initial success of the Greenland colony. When the coast of Greenland was warmer, the Vikings were able to grow crops and raise animals there. However, the regional climate gradually cooled, making farming more difficult. Without a reliable source of food, the Vikings were eventually forced to abandon their colony. 　

　　
First, the starvation theory. Even if agriculture became difficult, the Vikings still had an excellent source of food, the ocean. Historians used to think that the Vikings were unable or unwilling to fish, since they preferred to farm. But new evidence contradicts that idea. On fish. Since the supply of fish was not affected by the cooling climate. It seems unlikely that the Greenland Vikings would have starved or abandoned the colony for lack of food.

　　Second, the Vikings could have been driven out by other groups of people who also inhabited Greenland. Some of these groups came to Greenland before the Vikings did. The Vikings had to compete with them for the land and resources available in the region, and conflicts may have resulted. The Vikings likely would have been at a disadvantage when defending against populations that had been in Greenland longer and were better established there.

　　Second, it's unlikely that a conflict with another group forced the Vikings to leave. Archaeologists examining the remains of the colony found that the Vikings took all of the valuable objects away with them when they left the colony. This shows that the Vikings left the colony in an orderly way and had plenty of time to carefully pack their valuable belongings. If the colony had been attacked, the Vikings would have been forced to leave very quickly and would not have had time to pack up their valuables.

　　Third, a decline in trade with Europe could have caused the collapse of the Greenland colony. The colony initially traded directly and extensively with Europe, exchanging valuable animal products, such as walrus tusks, for European goods, such as metal tools. Later, however, the colony came under the control of Norway. The government of Norway forbade the colonists to trade with European traders and demanded that all Greenland products be transported to Norway first. The loss of direct trade with Europe would have made it much more difficult for the Greenland colonists to obtain the supplies they needed.

　　Third. A decline in trade with Europe. Well, even though official trade had to be conducted through Norway, there was still plenty of unofficial illegal trade. Many European traders ignored Norway's rules and continued to sail directly to Greenland to trade there. In fact, this illegal trade happened so frequently that the king of Norway himself complained about it. You see, we've discovered an actual document in which the king of Norway complained that the Greenland Vikings were trading so extensively with other countries that they had no good products left over to transport to Norway. All of this illegal trade probably provided enough supplies to the Greenland colony.

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主题：在撒哈拉沙漠发现的陨石是否来自水星（Mercury）

　　Color
The first clue about the meteorite's origin was its unusually light color. This quality suggested that the meteorite came from a planet with a thin, rocky outer crust and a hot interior core. The nearest planets fitting this description are Mercury, Venus, and Mars. Scientists ruled out Venus because its thick atmosphere would burn up any outgoing rocks. As for Mars, the Saharan meteorite looks nothing like any other meteorites known to be from Mars, so scientists ruled out Martian origins as well. That leaves Mercury as the most likely candidate.

　　Earth. It's true that the meteorite's light color suggests that it came from a planet with a rocky crust. But there are other options besides Mercury, Venus or Mars. You see. Early in the formation of the solar system, there were these objects, called protoplanets. The protoplanets had a crust and a core like today's planets. Most protoplanets do not exist anymore, however, because they kept colliding with one another. During these collisions, pieces of block broke off and were thrown into space. So the meteorite in the Sahara desert may not have come from any planet that's still in existence. Instead, it may be a piece of a protoplanet that was broken off long ago.

　　Magnetism

　　Second, one of the unique features of Mercury is that it has very low magnetism. Meteorites from other sources typically have very high magnetic intensity, but tests on the Saharan meteorite showed that it had the lowest level of magnetism ever measured in any meteorite. That level of magnetism almost perfectly matches that of Mercury's magnetic field. This close match to one of Mercury's unique traits provided strong evidence of its origin on Mercury.

　　Second yes, the low magnetism matches mercury's profile, but what's more important is the chemical composition of the meteorite. And that does not match up with the features of mercury. You see, the meteorite contains a large amount of a hard greenish mineral called pyroxine. And we don't know where that pyroxine came from, because studies have not found large amounts of that substance on mercury. So even though the magnetism data match, other features like the green thyroxine do not match.

　　Speed

　　Still, one puzzle remained. Mercury is the planet nearest to the Sun, so it was unclear how a rock from Mercury could travel all the way to Earth against the gravitational pull of the Sun. However, astronomers demonstrated through computer simulations that a collision with a space object could cause rocks to break off from Mercury at speeds fast enough to move away from the Sun's gravitational pull. It is therefore possible for a meteorite to make the journey from Mercury to Earth.

　　Finally, the journey from mercury to earth against the sun's gravitational pull, while possible, would require a lot of initial speed and energy. The rock would need to leave mercury at speeds of over nine kilometers per second, and that would cause it to become extremely hot. That type of heat would leave detectable signs on the rock. For example. The heat would cause some of the rock to melt to form glass, which means that we would find glass on the surface of the meteorite. But the Sahara meteorite doesn't have any glass. So it seems doubtful that it came from mercury.