TPO73阅读真题+题目+答案下载：Stellar Remnants

近期，ETS官方已经更新了TPO73，小编也是刚拿到TPO73，第一时间分享给广大的托福们，具体内容如下：

TPO73阅读真题+题目+答案下载：Stellar Remnants

Eventually,all stars consume their nuclear fuel and collapse into one of three final states-white dwarf,neutron star,or black hole.

White dwarfs are extremely small stars with densities greater than any known terrestrial material.It is believed that white dwarfs began life as low-mass or medium-mass stars.As the star ages,it begins to collapse-become a "dwarf-because it no longer produces sufficient radiant heat to counteract the contracting force of its gravity.Although some white dwarfs are no larger than Earth,the mass of such a dwarf can equal 1.4 times that of the Sun.A spoonful of such matter would weigh several tons.As a star contracts into a white dwarf, its surface becomes very hot and very bright.But,without a continuing source of energy,it will slowly become cooler and dimmer.Although none have been observed,the terminal stage of a white dwarf must be a small,cold, nonluminous body called a black dwarf.

A study of white dwarts produced what might at first appear to be a surprising conclusion:the smallest white dwarfs are the most massive,and the largest white dwarfs are the least massive.The explanation for this is that a more massive star has a greater gravitational force,and that greater gravitational force contracts the star into a smaller,more densely packed object than one gets with a less massive star.Thus,the smallest white dwarfs came from the collapse of stars that were larger and more massive than those the large white dwarfs came from.

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托福TPO73阅读题目：

1.The word "terminal"in paragraph 2 is closest in meaning to

A. best understood

B. least active

C. longest

D. final

2.It can be inferred from paragraph 2 that the reason white dwarfs have been observed and black dwarfs have not is that

A. there are more white dwarfs than black dwarfs

B. white dwarfs are larger than black dwarfs

C. white dwarfs are closer to Earth than are black dwarfs

D. white dwarfs emit light and black dwarfs do not

3.According to paragraph3amongstars thateventually became white dwarfs,why do the largest and most massive stars produce the smallest white dwarfs?

A. Only large,massive stars undergo several phases of collapse.

B. The more massive a star is,the more mass it loses as it collapses;so larger stars produce smaller dwarfs.

C. The gravitational force collapsing a star is greater for more massive stars;so the greater mass is compressed into a smaller volume.

D. One large star produces several small white dwarfs.

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