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A．comprising the least
B．composed of such minute
C．composed of very large
D．having so small number of
答案
更多“Astronomers have learned that the spectacular tails of comets are extremely tenuous bodies”相关的问题
第1题
What did eighteenth-century astronomers have in common with astronomers today？
A．They could not explain everything they detected with their instruments.
B．They knew the correct distances of objects they could not identify.
C．Their instruments were not powerful enough to detect spiral nebulae.
D．They argued over the natural brightness of variable stars.
第3题
A．problem
B．mystery
C．question
D．point
第4题
A．problem
B．mystery
C．question
D．point
第5题
A Star Is Born
1．The VLT (Very Large Telescope) is the wodd's largest telescope (望远镜) and is taking astronomers (天文学家) further back to the Big Bang than they ever thought possible. Located 2,600 metres up in the Chilean Andes, it has four huge mirrors, each about the size of a London bus. The VLT is so powerful it can spot a burning match 10,000 kilometres away.
2．This astonishing power will allow astronomers to see events in space from the birth of stars to the collision (碰撞) of galaxies (星系) on the edge of the cosmos (宇宙).The VLT is giving astronomers their best-ever view of the cosmos. The power of the VLT to see the smallest detail at the furthest distances makes its designers amazed.
3．Take the case of Eta Carinae, one of the most explosive stars in the universe. This star produces ultraviolet laser rays (紫外线) and it will destroy itself in a few million years' time. It is five times brighter than the sun and when it explodes it is going to be a sight worth waiting for!
4．But it is at distances of millions, even billions, of light years that the VLT really shows its power. The VLT can detect light that set out on its journey before the earth even existed. This gives astronomers their first-ever detailed views of events that took place in the earliest days of the cosmos.
5．In other words the VLT is a kind of a time machine. It takes astronomers back to a time when complete galaxies crashed into each other. The effects of these past collisions can now be seen by scientists, and astronomers believe the telescope will reveal more about these exciting events in the years to come. One day, we might be able to say we have traveled back to the beginning of time, and we will have a much clearer picture of how our planet was born.
第 23 题 Paragraph 1____________
第6题
A．He wants to book airline tickets.
B．He would like to have a cup of tea.
C．He is to leave for Shanghai.
D．He wants to make a reservation for dinner at the restaurant.
第7题
The finds of Geoffrey Marcy are frightening in that______.
A．it's the first time that astronomers have discovered such space entity
B．it substantially implies some kind of subversion to our present realization
C．it is an entire negation of the present astronomic research
D．they discovered the first extra-solar planet in astronomic study
第8题
Zhang Hong is said ______ by heart 2000 words up to now.
A．that she has learned
B．to have learned
C．to learn
D．having learned
第9题
根据下列文章,请回答 31～35 题。
Black Holes
What is a black hole？ Well, it's difficult to answer this question, since the terms we normally use to describe a scientific phenomenon are inadequate here. Astronomers and scientists think that a black hole is a region of space (not a thing) into which matter has fallen and from which nothing can escape -- not even light. So we can't see a black hole. A black hole exerts (施加) a strong gravitational (重力的) pull and yet it has no matter. It is only space -- or so we think. How can this happen？
The theory is that some stars explode ,when their density increases to a particular point; they "collapse" and sometimes a supernova (超新星) occurs. The collapse of a star may produce a "White Dwarf (白矮星) " or a "neutron star"-- a star whose matter is so dense that it continually shrinks by the force of its own gravity. But if the star is very large this process of shrinking may be so intense that a black hole results. Imagine the earth reduced to the size of a marble, but still having the same mass and a stronger gravitational pull, and you have some idea of the force of a black hole. Any matter near the black hole is sucked in. It is impossible to say what happens inside a black hole.
Our space and time laws don't seem to apply to objects in the area of a black hole. Einstein's relativity theory is the only one that can explain such phenomena. Einstein claimed that matter and energy are interchangeable, so that there is no "absolute" time and space. There are no constants at all, and measurements of time and space depend on the position of the observer -- they are relative. Einstein's theory provided a basis for the idea of black holes before astronomers started to find some evidence for their existence. It is only recently that astronomers have begun specific research into black holes.
The most convincing evidence of black holes comes from research into binary (由两部分组成的) star systems. In some binary star systems, astronomers have shown that there is an invisible companion star, a "partner" to the one which we can see in the sky. There is one star, called by its catalogue number HDE 226868, which must have a partner. This partner star, it seems, has a mass ten or twenty times greater than the sun-- yet we can't see it. Matter from HDE 226868 is being dragged towards this companion star. Could this invisible star, which exerts such a great force, be a black hole？ Astronomers have evidence of a few other stars too, which might have black holes as companions.
第 31 题 Which of the following does NOT fit the definition of the black hole？
A．The black hole is a region of space.
B．The black hole sucks in any object that passes by it.
C．The black hole is visible through an infrared telescope.
D．The black hole has no matter.
第10题
The last sentence implies that ______.
A．good management systems are essential
B．a great leader is all important
C．the more people, the better
D．big cities have no bright future
