gre阅读练习每日一篇(十八)_GRE阅读

gre阅读练习每日一篇(十八)

　　 Many visible stars are made to seem brighter than they really are.

　　 The presence of hydrogen and helium gas is revealed.

　　 The night sky appears dusty at all times to observers on Earth.

　　 The dust is conspicuously visible against a background of bright stars.

　　18. It can be inferred from the passage that the density of interstellar material is

　　 higher where distances between the stars are shorter

　　 equal to that of interstellar dust

　　 unusually low in the vicinity of our Sun

　　 independent of the incidence of gaseous components

　　 not homogeneous throughout interstellar space

　　19. It can be inferred from the passage that it is because space is so vast that

　　 little of the interstellar material in it seems substantial

　　 normal units of volume seem futile for measurements of density

　　 stars can be far enough from Earth to be obscured even by very sparsely distributed matter

　　 interstellar gases can, for all practical purposes, be regarded as transparent

　　 optical astronomy would be of little use even if no interstellar dust existed

　　In his 1976 study of slavery in the United States, Herbert Gutman, like Fogel, Engerman, and Genovese, has rightly stressed the slaves achievements. But unlike these historians, Gutman gives plantation owners little credit for these achievements. Rather, Gutman argues that one must look to the Black family and the slaves extended kinship system to understand how crucial achievements, such as the maintenance of a cultural heritage and the development of a communal consciousness, were possible. His findings compel attention.