Read the excerpt from Moon Mission. People first set foot on the moon on July 20, 1969. Astronauts Neil Armstrong and Buzz Aldrin stepped from the Apollo 11 spacecraft and planted an American flag on the moon's rocky surface. Six NASA lunar missions followed over the next few years, and 10 more astronauts walked the lunar surface. Then the United States government stopped funding such missions. NASA hasn't sent a crew to the moon since 1972. Which central idea is best supported by the excerpt details?