The correct order of key events regarding the exploration of space, beginning with the earliest, is:
- First humans in space (Yuri Gagarin in 1961)
- First space shuttle flight (1981)
- First humans on the Moon (Apollo 11 in 1969)
- First lander on Mars (Viking 1 in 1976)
- Launching of the International Space Station (1998)
- First humans on Mars (this event has not yet occurred as of my last knowledge update in October 2023)
Therefore, the closest matching option in the given responses would be: first humans in space, first space shuttle flights, first humans on the moon. If you're looking at actual historical events though, keep in mind that the "first humans on Mars" has not happened yet.