12.Practice.Tests.for.the.SAT_2015-2016_1128p

Section 41
Practice Test Seven 609
Questions 10-15 are based on the following passage.
There has been a great deal of scientific speculation about
what caused the extinction of the dinosaurs. The fo llowing
passage presents recent developments affecting this debate.
The question of why dinosaurs became
extinct has puzzled paleontologists since the first
dinosaur fossil was found almost two centuries
Line ago. These great reptiles dominated the earth for
(5) almost 160 million years but mysteriously died
out approximately 65 million years ago. Various
explanations for this disappearance have been
offered, ranging from an epidemic to a sudden,
catastrophic drop in temperature, but definitive
(10) proof has remained elusive.
In 1980, Luis Alvarez, winner of the Nobel Prize
in Physics, suggested a novel explanation: cosmic
extinction. According to Alvarez and his geologist
son Walter, a huge meteor crashed into the earth's
(15) surface 65 million years ago, sending up a massive
cloud of dust and rock particles. The cloud
blocked out sunlight for a period of months or
even years, disrupting plant photosynthesis and, by
extension, the global food chain. The lack of vege-
(20) tation, coupled with a significant drop in temperature,
resulted in the extinction of the dinosaurs.
Alvarez based his theory on a curious piece of
evidence:.the presence of a thin layer of iridium
that had recently been discovered in geologic sedi-
(25) ments laid down at approximately the time the
dinosaurs died out. The metal iridium is rarely
found on the earth's surface; Alvarez reasoned
that it had either come up from the earth's core
by volcanic action or been deposited from space
(30) through the fall of one or more meteorites. He
found the latter explanation more likely, given the
even distribution of the iridium layer worldwide.
But paleontologists scoffed at the Alvarez extinction
theory. Neither Luis nor Walter Alvarez was
(35) a paleontologist, yet they claimed to have solved a
mystery that had defied the efforts of paleontologists
for over a century. Professional hostility was
also fueled by the somewhat abrasive style of the
elder Alvarez. But the most important objection
( 40) to the Alvarez theory was evidential. In order to
create worldwide fallout on the scale suggested by
Alvarez, the "doomsday" meteorite would have
had to be on the order of five miles in diameter; its
impact would have formed a crater perhaps
( 45) a hundred miles wide. Where was the crater?
Finally, a decade after the cosmic extinction
theory was first proposed, the crater was found.
Lying on the northern edge of Mexico's Yucatan
Peninsula, the crater is 110 miles wide. Long
(50) buried under sediment, it had actually been discovered
in 1981 by oil geologists, but datings of
nearby rock samples taken at that time suggested
that it was significantly older than 65 million
years. New samples of melted rock from the crater
(55) itself were recently analyzed by an advanced dating
process, however, and were found to be 64.98
million years old. Many scientists now feel that,
thanks to the Alvarez theory, the mystery of dinosaur
extinction has finally been solved.
10. The word "elusive" in line 10 most nearly means
(A) evasive
(B) hard to understand
(C) difficult to find
(D) rare
(E) questionable
11. The author indicates that opponents of the Alvarez
theory criticized both Luis and Walter Alvarez for
(A) publishing incomplete research
(B) being personally abrasive
( C) theorizing outside their own fields
(D) misinterpreting experimental data
(E) using improper investigative methods
12. The word "novel" is used in line 12 to mean
(A) original
(B) strange
(C) eccentric
(D) controversial
(E) fictitious
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