評論
打印
11. AMENITY : COMFORTABLE
(A) tact : circumspect
(B) nuisance : aggravated
(C) honorarium :grateful
(D) favorite : envious
(E) lounge : patient
12. PAIN : ANALGESIC::
(A) energy : revitalization
(B) interest : stimulation
(C) symptom : palliative
(D) despair : anxiety
(E) reward : incentive
13. VOICE:SHOUT::
(A) ear : overhear
(B) eve : see
(C) hand : clutch
(D) nerve : feel
(E) nose : inhale
14. PONTIFICATE: SPEAK::
(A) strut : walk
(B) stare : look
(C) patronize : frequent
(D) eulogize : mourn
(E) reciprocate : give
15. BIBLIOPHILE : BOOKS::
(A) environmentalist : pollution
(B) zoologist : animals
(C) gourmet : food
(D) calligrapher : handwriting
(E) aviator : aircraft
16. INDIGENT : WEALTH::
(A) presumptuous : independence
(B) imperturbable : determination
(C) inevitable : inescapability
(D) indigestible : sustenance
(E) redundant : indispensability
This passage is based on an article published in 1990.
Eight times within the pat million years, some-
thing in the Earth’s climatic equation has changed.
allowing snow in the mountains and the northern
Line latitudes to accumulate from one season to the next
(5) instead of melting away. Each time, the enormous ice
sheets resulting from this continual buildup lasted tens
of thousands of years until the end of each particular
glacial cycle brought a warmer climate. Scientists
speculated that these glacial cycles were ultimately
(10) driven by astronomical factors: slow, cyclic changes
in the eccentricity of the Earth’s orbit and in the tilt
and orientation of its spin axis. But up until around
30 years ago, the lack of an independent record of ice-
age timing made the hypothesis untestable.
(15) Then in the early 1950’s Emiliani produced the
first complete record of the waxings and wanings
of past glaciations. It came from a seemingly odd
place. the seafloor. Single-cell marine organisms
called "foraminifera" house themselves in shells made
(20) from calcium carbonate. When the foraminifera die.
sink to the bottom, and become part of seafloor sedi-
ments, the carbonate of their shells preserves certain
characteristics of the seawater they inhabited. In
particular, the ratio of a heavy, isotope of oxygen
(25) (oxygen-18) to ordinary oxygen (oxygen- 16) in the
carbonate preserves the ratio of the two oxygens in
water molecules.
It is now understood that the ratio of oxygen iso-
topes in seawater closely reflects the proportion of
(30) the world’s water locked up in glaciers and ice sheets.
A kind of meteorological distillation accounts for the
link. Water molecules containing the heavier isotope
tend to condense and fall as precipitation slightly
sooner than molecules containing the lighter isotope.
(35) Hence, as water vapor evaporated from warm oceans
moves away from its source. its oxygen -18 returns
more quickly to the oceans than does its oxygen-16.
What falls as snow on distant ice sheets and mountain
glaciers is relatively depleted of oxygen -18. As the
(40) oxygen-18-poor ice builds up the oceans become
relatively enriched in the Isotope. The larger the ice
sheets grow, the higher the proportion of oxygen-18
becomes in seawater- and hence in the sediments.
Analyzing cores drilled from seafloor sediments,
(45) Emiliani found that the isotopic ratio rose and fell in
rough accord with the Earth’s astronomical cycles.
Since that pioneering observation, oxygen-isotope
measurements have been made on hundreds of cores
A chronology for the combined record enables scien-
(50) tists to show that the record contains the very same
periodicities as the orbital processes. Over the past
800,000 years, the global ice volume has peaked
every 100,000 years, matching the period of the
orbital eccentricity variation. In addition, “wrinkles”
(55) superposed on each cycle –small decreases or surges
in ice volume – have come at intervals of roughly
23,000 and 41,000 years, in keeping with the pre-
