d) Skylab

Skylab was America’s first space station and marked a significant milestone in space exploration history. Launched in 1973 by NASA, Skylab was a major step in long-duration space missions, allowing astronauts to conduct scientific experiments in orbit for extended periods. The space station included a workshop, solar observatory, and living quarters for its crew. Skylab missions contributed valuable data on the effects of long-term spaceflight on the human body and on various scientific disciplines. Despite challenges, including damage during launch, Skylab was a successful program that paved the way for future space stations like the International Space Station.