The correct order of key events regarding the exploration of space is:
first humans in space, first humans on the moon, first space shuttle flight.
This sequence would be:
- First humans in space (Yuri Gagarin, 1961)
- First humans on the moon (Apollo 11, 1969)
- First space shuttle flight (STS-1, 1981)
So the correct response from your list would be:
first humans in space, first space shuttle flights, first humans on the moon.