70. a. wise b. clever c. slow d. enough
Reading
Comprehension
A
A scientist in Israel has
introduced a new theory that explains the mass extinction of the dinosaurs 65
million years ago. The scientist believes the criminal was deadly radiation
caused by the collision of two stars.
Arnon
Dar, a physicist at Technion
University, says stars
collide every day somewhere in the universe. Those collisions produce
radiation-gamma and cosmic rays----with the potential to destroy the protective
layers of Earth’s atmosphere and kill most animal and plant life.
Usually,
the collisions are too distant to do any damage to life on earth. But once
every 100 million years or so, stars collide relatively close to Earth. A
nearby collision could have emitted enough gamma and cosmic rays to kill the
dinosaurs, the scientist says. Star collisions could also have been the cause
of the five other mass extinctions that have happened on Earth, he adds. The
most severe die-off, which killed 95 percent of all life, happened about 225
million years ago.
To
support his idea, the scientist is now looking through layers of ancient rock
for mineral that show evidence of being bombarded by cosmic radiation 65
million years ago.