Line chart indicating the population, in millions, from 1900 to 2000. The carrying capacity is indicated with a horizontal line around 200 million. The population grows at a steady and rapid rate, intersecting the dotted line between 1970 and 1980. According to the graph, during which decade did the U.S. population reach carrying capacity? The 1990s The 1970s The 1960s The 1980s