As observed from the Earth，the angle between lines from the

共用题干
The Mysteries of Nazca

In the desert of Peru,300 kilometers from Lima,one of the most unusual artworks in the world has
mystified（迷惑）people for decades._________(46 ) But from high above,these marks are huge images of
birds,fish,seashells,all beautifully carved into the earth.
The Nazca lines are so difficult to see from the ground that they weren't discovered until the 1930s,
when pilots spotted them while flying over the area. In all,there are about 70 different human and animal
figures on the plain,along with 900 triangles,circles,and lines.
Researchers have figured out that the lines are at least 1,500 years old,but their purpose is still a
mystery._________(47)However,it would probably be very tricky to land a spaceship in the middle of
pictures of dogs and monkeys.
In the 1940s,an American explorer named Paul Kosok suggested that the drawings are a chronicle(己
录）of the movement of the stars and planets._________(48)Later,an astronomer tested his theory with a
computer,but he couldn't find any relation between the lines and movements in space.
Another explanation is that the lines may have been made for religious reasons.British researcher Tony
Morrison investigated the customs of people in the Andes Mountain and learned that they sometimes pray by
the side of the road.It's possible that in the past,the lines of Nazca were created for a similar purpose.
_________(49)But the local people have never constructed anything this big.
Recently,two other scientists,David Johnson and Steve Mabee,have speculated that lines could have
been related to water. Nazca is one of the driest places in the world and receives only 2cm of rain every year.
While Johnson was searching for ancient water sources in the area,he noticed that some waterways built by
ancient people were connected with the lines.Johnson believes that the Nazca lines are a giant map of the
underground water in the area._________（50)

_________(46)
A:Other scientists are now searching for evidence to prove this.
B: A Swiss writer named Erich Von Daniken wrote that the Nazca lines were designed as a landing place for UFOs.
C:Scholars differ in interpreting the purpose of the designs.
D:The largest pictures may have been the sites for special ceremonies.
E:Seen from the ground,it looks like lines scratched into the earth.
F: He called Nazca"the largest astronomy book in the world".

共用题干
Weight on and off the Earth We are so used to.our life on the surface of the earth that it can be quite an effort for our mind to break free of all the ideas that we take for granted.Because we can feel that things are heavy,we think of "weight"as being a fixed quality in an object,but it is not really fixed at all.If you could take a one-pound packet of butter 4,000 miles out from the earth,it would weigh only a quarter of a pound. Why would things weigh only a quarter as much as they do at the surface of the earth if we took them 4,000 miles out into space?The reason is this:all objects have a natural attraction for all other objects;this is called gravitational attraction.But this power of attraction between two obects gets weaker as they get farther apart.When the butter was at the surface of the earth,it was 4,000 miles from the center.When we took the butter 4,000 miles out,it was 8,000 miles from the center,which is twice the distance.If you double the distance between two objects,their gravitational attraction decreases two times two.If you treble the distance, it gets nine times weaker(three times three)and so on. So this is one of the first things we need to remember that the weight of an object in space is not the same as its weight on the surface of the earth. What about the weight of our pound of butter on the surface of the moon?At the distance the puii of the earth is about 4,000 times smaller than it is here on the surface,so we can forget all about the earth-pull on our butter. On the other hand,on the moon there will be an attraction between the butter and the moon,but the butter will weigh only about one-sixth as much as it does on the earth.This is because the moon is so much smaller than the earth.The amount of gravitational pull that a body produces depends on the amount of material in it.A packet of butter has a gravitational pull of its own;but this is very small in relation to the pull of something as large as the moon,or the earth,or the sun.

The main idea of this passage is
A:different weight systems in different places
B:freedom from traditional ideas
C:traveling from the earth to the moon
D:the effect of gravitation on weight

共用题干
Weight on and off the Earth We are so used to.our life on the surface of the earth that it can be quite an effort for our mind to break free of all the ideas that we take for granted.Because we can feel that things are heavy,we think of "weight"as being a fixed quality in an object,but it is not really fixed at all.If you could take a one-pound packet of butter 4,000 miles out from the earth,it would weigh only a quarter of a pound. Why would things weigh only a quarter as much as they do at the surface of the earth if we took them 4,000 miles out into space?The reason is this:all objects have a natural attraction for all other objects;this is called gravitational attraction.But this power of attraction between two obects gets weaker as they get farther apart.When the butter was at the surface of the earth,it was 4,000 miles from the center.When we took the butter 4,000 miles out,it was 8,000 miles from the center,which is twice the distance.If you double the distance between two objects,their gravitational attraction decreases two times two.If you treble the distance, it gets nine times weaker(three times three)and so on. So this is one of the first things we need to remember that the weight of an object in space is not the same as its weight on the surface of the earth. What about the weight of our pound of butter on the surface of the moon?At the distance the puii of the earth is about 4,000 times smaller than it is here on the surface,so we can forget all about the earth-pull on our butter. On the other hand,on the moon there will be an attraction between the butter and the moon,but the butter will weigh only about one-sixth as much as it does on the earth.This is because the moon is so much smaller than the earth.The amount of gravitational pull that a body produces depends on the amount of material in it.A packet of butter has a gravitational pull of its own;but this is very small in relation to the pull of something as large as the moon,or the earth,or the sun.

According to the passage,"weight"should be understood in the sense that
A:it is fixed if it is outside the earth's gravitational puli
B:it decreases four times when it is 4,000 miles from the earth's center
C:it varies with the change of the gravitational attraction between two objects
D:things increase in amount as they are closer to the earth's surface

There are no__________ differences between the two products, despite the fact that each is made from different materials.

A.observably
B.observing
C.observe
D.observable

The rising sun is especially beautiful to look at from this angle.

A:particularly
B:obviously
C:apparently
D:expressively

共用题干
Where Did the Earth's Water Come From?

Earth is located within the"snow line"of the solar system,the region closest to the Sun where H2 0 is primarily in liquid or gaseous form,if at all.______(46)The snow line phenomena is reflected in the water content of planets like Mercury,Venus,and Mars. Water is absent on Mercury.On Venus,H₂O only exists as a trace element in the atmosphere.Mars only has a thin veneer of ice in its polar regions.In general,water is rare within the snow line.
Why does Earth have so much water relative to the other inner planets?71%of the surface is covered in the oceans,more than half of which is deeper than 3,000 meters,with an approximate total volume of 1.3 billion cu km.______(47)
There are various theories as to where all the Earth's water came from,but several theories have fared better than the others.______(48)When the Earth was in the process of forming,with a radius just 40%smaller than at present,it would have had enough gravity to hold on to a tenuous atmosphere with water vapor. The first water vapor on the planet would have come from the planet's internals,where volatile(low weight)chemicals would have a tendency to float to the top,and heavy chemicals(iron and nickel)would sink.
Though the first of Earth's water came about through volcanism,this alone probably didn't produce enough to form stable pools on the surface.______(49)Comparing the isotope ratios of water on Earth and water from comets and asteroids has revealed that the majority of the Earth's water comes from asteroids.
Throughout its history,Earth's water has increased in volume due to biological processes. In the early seas of Earth,hydrogen sulfide would have been in great supply,which,when reacted with carbon dioxide from the atmosphere during photosynthesis in sulfide-reducing bacteria,would have produced hydrogen,sulfur,and water.______(50)

________（49）
A: More water was added to the planet during several hypothesized large impacts from asteroids from the outer asteroid belt.
B:We know that the oceans existed as early as 100 million years after the formation of the Earth.
C:Still,the oceans only make up 0.023%of the Earth's total mass.
D:Astronomers say Earth s water may have come from space.
E:The snow line is located in the outerasteroid belt,between the orbits of Mars and Jupiter.
F: Many geologists believe that the majority of Earth's water generated through this process.