The Apollo Space Program 1 Apollo's Moon mission was one of the biggest challenges that the government had undertaken. Over 34,000 NASA employees and 375,000 outside contractors took part in the Apollo program to make the dream of walking on the Moon come true. The Apollo program began as a "space race" between the United States and the Soviet Union (present-day Russia). However, President Kennedy surprised the world by suggesting that the two countries would work together to fulfill the world's dream of exploring the Moon.

2 NASA had planned a total of 17 Apollo missions. At the beginning, most Apollo missions focused on successfully orbiting the Earth. However, many of those missions failed. On October 11, 1968, following several unmanned Earth-orbit flights, Apollo 7 successfully orbited the Earth 163 times. Apollo 7 carried a full crew of three astronauts. Later, Apollo 8 took the the first step toward manned lunar exploration. Apollo 9 carried out a long mission around Earth's orbit to check if the Lunar Module functioned properly. Apollo 10 journeyed to the lunar orbit and tested the Lunar Module to within 15.2 km of the Moon's surface. Finally, in July 1969, Apollo 11 performed the step-by-step procedure and landed on the Moon. On July 20, astronaut Neil Armstrong became the first human to set foot on the Moon's surface.
3 The Apollo 13 was launched in April 1970, but it suffered an accident from an oxygen tank explosion because of which it had to safely return to Earth. The other Apollo missions that followed conducted several experiments on the Moon's surface and even collected 842 pounds of Moon rock. Apollo 17 was the final Apollo mission that took place in December 1972. In total, there were six successful Moon landings, and twelve American astronauts walked on the Moon.
4 The Apollo Space Program proved to the world that manned space exploration was a real possibility. The current space programs are only at an intermediate stage of development, but soon, they will advance to help humans walk on not just the Moon but possibly on different planets.
1
How does the author organize the selection?
A.
By describing the Apollo Space Program and the different Apollo missions that advanced to put astronauts in space and study the Moon
B.
By comparing the old Apollo missions that only orbited around Earth to the newer Apollo missions that landed on the Moon and studied the surface
C.
By explaining why scientists wanted to study the Moon and the way they designed the Apollo lunar modules to carry astronauts to space
D.
By summarizing the main problem with the failed Apollo missions and then narrating how scientists solved the problem with the oxygen tanks