Read' each passage and' choose the best answer ll'rom among the 1llour cho'ces Iller eacll quest'on.Tlhen,on your answer sheet, find the number of the question andl markyoしIr answe'.
The North American Big Bang?
A team of scientists is now arguing that the giant mammals of
North America went out with a bang-1itera11y.The culprit is believed to have been a comet that collided with earth about 13,000 years ago, triggering an initial wave of heat that swept across the continent,ignited massive fires,and sent clouds of debris into the atmosphere.According to the researchers,overt7 species-including woolly mammoths, saber-toothed tigers,and giant ground sloths - were wiped out by the blast,the wave of heat it caused,and an ensuing cold period.