[ 111 ] Earth and Space Science GED ® TEST SCIENCE FLASH REVIEW • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Refer to the following passage to answer the next four questions. Ocean acidification occurs when seawater absorbs carbon dioxide from the atmosphere. This causes the water to become more acidic. Dissolved carbon dioxide increases the hydrogen ion concentration in the ocean, which decreases the ocean’s pH level. Calcifying organisms such as corals, oysters, and sea urchins find it more difficult to build shells and skeletons in acidic water. Carbon dioxide in the atmosphere comes from many sources. When humans burn oil or gas to generate power, carbon dioxide is released. Carbon dioxide is also a greenhouse gas, which means it leads to warmer temperatures on Earth’s surface by trapping heat in the air. Atmospheric CO 2 at Mauna Loa Observatory 400 Scripps Institution of Oceanography NOAA Earth System Research Laboratory 380 Parts per Million 360 340 320 1960 1970 1980 1990 2000 2010 Year January 2011 Based on the graph and the information from the passage, what year presented the lowest risk of ocean acidification? A. 1960 B. 1970 C. 1990 D. 2010