GWD-4-Q35，没有讨论过。难道大家都没疑问？？

howardwang

GWD-4-Q35 to GWD-4-Q37:

      In addition to conventional

       galaxies, the universe contains

       very dim galaxies that until

Line recently went unnoticed by

  (5)       astronomers.  ossibly as

numerous as conventional gal-

axies, these galaxies have the

same general shape and even

the same approximate number

(10) of stars as a common type of

conventional galaxy, the spiral,

but tend to be much larger.

Because these galaxies’

mass is spread out over

(15)      larger areas, they have far

fewer stars per unit volume

than do conventional galaxies.

Apparently these low-surface-

brightness galaxies, as they

(20)      are called, take much longer

       than conventional galaxies to

       condense their primordial gas

and convert it to stars—that is,

they evolve much more slowly.

(25)            These galaxies may

constitute an answer to the long-

standing puzzle of the missing

baryonic mass in the universe.

Baryons—subatomic particles

(30)      that are generally protons or

neutrons—are the source of

stellar, and therefore galactic,

       luminosity, and so their numbers

can be estimated based on how

(35)       luminous galaxies are.  How-

ever, the amount of helium

in the universe, as measured

by spectroscopy, suggests

      that there are far more baryons

(40)     in the universe than estimates

based on galactic luminosity

indicate.  Astronomers have

long speculated that the missing

baryonic mass might eventually

(45)      be discovered in intergalactic

space or as some large popu-

lation of galaxies that are difficult

to detect.

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GWD-4-Q35:

The primary purpose of the passage is to

              

describe a phenomenon and consider its scientific significance

contrast two phenomena and discuss a puzzling difference between them

identify a newly discovered phenomenon and explain its origins

compare two classes of objects and discuss the physical properties of each

discuss a discovery and point out its inconsistency with existing theory

答案是A.

我怎么看不出来在那里consider its scientific significance？

C为何不对？

billyxiangLi

个人愚见 关于purpose题主要看文章后面

说的就是关于发现了这新星系后，能合理解释B的遗失问题

carolhide

These galaxies may

constitute an answer to the long-

standing puzzle of the missing

baryonic mass in the universe.

its scientific significance就在这里，解决了个长时间存在的难题。