Read the selection below. Then carefully consider the questi…

Read the selection below. Then carefully consider the question that follow and choose the best responses. Geologists study rocks. Archaeologists study old civilizations. And atmospheric chemists—the newest breed of scientist—study old air, the kind trapped in bubbles found in glaciers left over from the last ice age or in the ice sheets of Greenland or Antarctica. By studying the history of our atmosphere, these scientists can tell what the air was like in prehistoric times and measure how human activity over two thousand years has changed it. First the ice is cut into cubes, and then the air is sucked out into a vacuum chamber where it is stored in tubes. Finally, the carbon dioxide level is analyzed by a laser beam. It is believed that rising levels of carbon dioxide foretell a rise in temperatures around the world. Thus these scientists may be able to predict dangerous changes in climate and possibly the next ice age. The tone of this paragraph can be described as