The correct answer is option 1: High altitude. The South Pole is colder than the North Pole primarily because of its higher altitude. Altitude refers to the height above sea level, and the South Pole is located at a higher altitude than the North Pole. At higher altitudes, the air is less dense, which means that it can hold less heat. This results in lower temperatures. In contrast, the North Pole is located at a lower altitude, so the air is denser and can hold more heat. Additionally, the South Pole is located on the Antarctic continent, which is covered with ice and snow year-round. This helps to further lower the temperature. While options 2, 3, and 4 may have some influence on the overall climate at the poles, they are not the main factors that make the South Pole colder than the North Pole.