The key answer of exercise 7

The astronauts kept the flag in a thin tube, so when they took it out it seemed to wave. The landings happened in the morning and the stars were not bright enough - that's why they weren’t visible. The surface of the moon is covered by dust. When the module landed on the moon, the engines blew the dust away and it didn’t leave any traces. If landing on the moon had been a fake astronaut from the other countries would have discovered it and found the proof long ago. About 40,000 people worked on the mission. It wouldn’t have been possible for all the people to keep the secret.