1. Only recently have investigators considered using the plants to clean up soil and waste sites that have been contaminated by toxic levels of heavy metals–an environmentally friendly approach known as phytoremediation. This scenario begins with the planting of hyperaccumulating species in the target area, such as an abandoned mine or an irrigation pond contaminated by runoff. Toxic minerals would first be absorbed by roots but later relocated to the stem and leaves. A harvest of the shoots would remove the toxic compounds off site to be burned or composted to recover the metal for industrial us. After veral years of cultivation and harvest, the site would be restored at a cost much lower than the price of excavation and reburial, the standard practice for remediation of contaminated soils. For examples, in field trials, the plant alpine pennycress removed zinc and cadmium from soils near a zinc smelter, and Indian mustard native to Pakistan and India, has been effective in reducing levels of lenium salts by 50 percent in contaminated soils.
逻辑训练
权的形近字Why does the author mention “Indian mustard”?
A. To warn about possible risks involved in phytoremediation.
B. To help illustrate the potential of phytoremediation.
C. To show that hyperaccumulating plants grow in many regions of the world.
D. To explain how zinc contamination can be reduced.
2. The great height of Martian volcanoes is a direct conquence of the planet’s low surface gravity. As lava flows and spreads to form a shield volcano, the volcano’s eventual height depends on the new mountain’s ability to support its own weight. The lower the gravity, the lesr the weight and the greater the height of the mountain. It is no accident that Maxwell Mons on Venus and the Hawaiian shield volcanoes on Earth ri to about the same height (about 10 kilometers) above their respective bas-Earth and Venus have similar surface gravity. Mars’s surface gravity is only 40 percent that of Earth, so volcanoes ri roughly 2.5 times as high. Are the Martian shield volcanoes still active? Scientists have no direct evidence for recent or ongoing eruptions, but if the volcanoes were active as recently as 100 million years ago (an estimate of the time of last eruption bad on the extent of impact cratering on their slopes), some of them may still be at leas
t intermittently active. Millions of years, though, may pass between eruptions.
In paragraph 3, why does the author compare Maxwell Mons on Venus to the Hawaiian shield volcanoes on Earth?
A. To help explain the relationship between surface gravity and volcano height.
B. To explain why Mars’s surface gravity is only 40 percent of Earth’s.
C. To point out differences between the surface gravity of Earth and the surface gravity of Venus.小米儿童电话手表
D. To argue that there are more similarities than differences between volcanoes on different planets.
3.Cuneiform texts on science, astronomy, medicine, and mathematics abound, some offering astoundingly preci data. One tablet records the speed of the Moon over 248 days; another documents an early sighting of Halley's Cornet, from September 22 to Sept
ember 28, 164 B.C.E.炒肝赵 More esoteric texts attempt to explain old Babylonian customs, such as the procedure for curing someone who is ill, which included rubbing tar and gypsum on the sick person's door and drawing a design at the foot of the person's bed. What is clear from the vast body of texts (some 20,000 tablets were found in King Ashurbanipal's library at Nineveh) is that scribes took pride in their writing and knowledge.
Why does the author mention a cuneiform text that documents "an early sighting of Halley's Cornet, from September 22 to September 28, 164 B.C.E.”?西安旅游必去景点推荐
兔子简单画法A. To explain how important Babylonian events were recorded.
B. To support the idea that some cuneiform texts provide preci scientific information.
C. To explain how particular Babylonian customs aro concerning sick persons.
D. To identify a particularly valuable text from the library of King Ashurbanipal.
4. 杨的成语While many other obrvers and thinkers had laid the groundwork for science, Thales (circa 624 B.C.E-ca 547 B.C.E.), the best known of the earliest Greek philosophers, made the first steps toward a new, more objective approach to finding out about the world. He pod a very basic question: "What is the world made of? " Many others had asked the same question before him, but Thales bad his answer strictly on what he had obrved and what he could reason out-not on imaginative stories about the gods or the supernatural. He propod water as the single substance from which everything in the world was made and developed a model of the univer with Earth as a flat disk floating in water.
