题目内容
______ they reached the small village before dusk.
a. Towards the end b. By the end c. In the end d. At the end
C
|
Only after they had discussed the matter for several hours ______ an agreement.
A.they reached | B.do they reach |
C.they reach | D.did they reach |
The temperature of the sun is over 5000 degrees Fahrenheit at the surface, but it rises to perhaps more than 16 million degrees at the center.The sun is so much hotter than die earth that matter can exist only as a gas, except at the core.In the core of the sun, the pressures are so great against the gases that, despite the high temperature, there may be a small solid core.However, no one really knows, since the center of the sun can never be directly observed.
Solar astronomers do know that the sun is divided into five layers or zones.Starting at the outside and going down into the sun, the zones are the corona, chromosphere, photosphere, convection zone and finally the core.The first three zones are regarded as the sun's atmosphere.
But since the sun has no solid surface, it is hard to tell where the atmosphere ends and the main
body of the sun begins.
The sun's outermost layer begins about 10000 miles above the visible surface and goes outward for mllions of miles.This is the only part of the sun that can be seen during an eclipse(日食) such as the one in February 1979.At any other time, the corona can be seen only when special instruments are used on cameras and telescopes to shut out the glare of the sun's rays.
The corona is a brilliant, pearly white, filmy light, about as bright as the full moon.Its beautiful rays are a sensational sight during an eclipse.The corona's rays flash out in a brilliant fan that has wispy spikelike(一束束穗状) rays near the sun's north and south poles.The corona is thickest at the sun's equator.
The corona rays are made up of gases streaming outward at tremendous speeds sad reaching a temperature of more than 2 million degrees Fahrenheit.The rays of gas thin out as they reach the space around the planets.By the time the sun's corona rays reach the Earth, they are weak and invisible.
【小题1】Matter on the aim can exist only in fee form of gas because of the sun's ___.
A.size | B.age | C.location | D.temperature |
A.corona | B.chromosphere | C.photosphere | D.core |
A.hotter | B.clearer | C.thinner | D.stronger |
A.The remaining layers of the sun. |
B.The evolution of the sun to its present form. |
C.The eclipse of February 1979. |
D.All the above. |
Why do men die earlier than women? The latest research makes it known that the reason could be that men’s hearts go into rapid decline when they reach middle age.
The largest study of the effects of ageing on the heart has found that women’s longevity may be linked to the fact that their hearts hardly lose their pumping power with age.
“We have found that the power of the male heart falls by 20---25 percent between 18 and 70 years of age,” said the head of the study, David Goldspink of Liverpool John Moores University in the UK. “Within the heart there are millions of cells that enable it to beat. Between the age of 20 and 70, one-third of those cells die and are not replaced in men,” said Goldspink. “This is part of the ageing process.”
What surprises scientists is that the female heart sees very little loss of these cells. A healthy 70-year-old woman’s heart could perform almost as well as a 20-year-old one’s.
“This gender (性别)difference might just explain why women live longer than men,” said Goldspink.
They studied more than 250 healthy men and women between the ages of 18 and 80, focusing on healthy persons to remove the confusing influence of disease.
The team has yet to find why ageing takes a greater loss on the male heart, said Goldspink.
The good news is that men can improve the health of their heart with regular exercise. Goldspink stressed that women also need regular exercise to prevent their leg muscles becoming smaller and weaker as they age.
【小题1】The underlined word “longevity” in the second paragraph probably refers to _________.
A.health | B.long life | C.ageing | D.effect |
A.men’s heart cells | B.women’s ageing process |
C.the gender difference | D.hearts and long life |
A.women have more cells than men when they are born |
B.women can replace the cells that enable the heart to beat |
C.the female heart loses few of the cells with age |
D.women never lose their pumping power with age |
A.the reason why ageing takes a greater loss on the male heart has been found out |
B.scientists are on the way to finding out why the male heart loses more of the cells |
C.the team has done something to prevent the male from suffering the greater loss |
D.women over 70 could lose more heart cells than those at the age of 20 |
Only after they had discussed the matter for several hours a decision .
A.they reached |
B.did they reach |
C.they reach |
D.do they reach |