Millions of stars are travelling about in space. A few form groups which journey together, but most of them travel alone. And they travel through a universe so large that one star seldom comes near to another.
We believe, however, that some two thousand million years ago, another star wandering through space, happened to come near our sun. Just as the sun and the moon raise tides on the earth, so this star must have raised tides on the surface of the sun. But they were very different from the small tides that are raised in our oceans; a large tidal wave must have travelled over the surface of the sun, at last forming a mountain so high that we cannot imagine it. As the cause of the disturbance (动荡) came nearer, so the mountain rose higher and higher. And before the star began to move away again, its tidal pull had become so powerful that this mountain was torn to pieces and threw off small parts of itself into space. These small pieces have been going round the sun ever since. They are the planets (行星).

The expression "the cause of the disturbance" in paragraph 2 refers to （　）

A:the large tidal wave B:the powerful tidal pull C:the star coming near the sun D:one of the sun’s planets

Millions of stars are traveling about in space. A few form groups which journey together, but most of them travel alone. And they travel through a universe so large that one star seldom comes near to another.
We believe, however, that some two thousand million years ago, another star wandering through space, happened to come near our sun. Just as the sun and the moon raise tides on the earth, so this star must have raised tides on the surface of the sun. But they were very different from the small tides that are raised in our oceans; a large tidal wave’ must have travelled over the surface of the sun, at last forming a mountain so high that we cannot imagine it. As the cause of the disturbance (动荡) came nearer, so the mountain rose higher and higher. And before the star began to move away again, its tidal pull had become so powerful that this mountain was torn to pieces and threw off small parts of itself into space. These small pieces have been going round the sun ever since. They are the planets (行星).
The expression "the cause of the disturbance" in paragraph 2 refers to______.

A:the large tidal wave B:the powerful tidal pull C:the star coming near the sun D:one of the sun’s planets

Passage Four

The expression "the cause of the disturbance" in paragraph 2 refers to______.

A:the large tidal wave B:the powerful tidal pull C:the star coming near the sun D:one of the sun’s planets

Please ______ that shop over there and I will go in and ask for directions.

A:pull in at B:pull at C:pull out at D:pull in

Mr. Smith's condition looks serious and it is doubtful if he will ______.

A:pull through B:pull up C:pull back D:pull out

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 objects 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 from the center, which is twice the distance. If you double the distance between two objects, their gravitational attraction decreases four times (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 pull 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 pull 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

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 objects 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 from the center, which is twice the distance. If you double the distance between two objects, their gravitational attraction decreases four times (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 pull 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.

We do not feel the gravitational pull of a packet of butter because （　）.

A:it is too small to have a gravitational pull of its own B:its pull is so small that we tend to ignore it C:its pull disappears in the presence of the earth’s gravitation D:it tends to melt and loses its gravitational pull

We do not feel the gravitational pull of a packet of butter because

A:it is too small to have a gravitational pull of its own. B:its pull is so small that we tend to ignore it. C:its pull disappears in the presence of the earth's gravitation. D:it tends to melt and loses its gravitational pull.

We do not feel the gravitational pull of a packet of butter because

A:it is too small to have a gravitational pull of its own. B:its pull is so small that we tend to ignore it. C:its pull disappears in the presence of the earth's gravitation. D:it tends to melt and loses its gravitational pull.