The correct order of key events regarding the exploration of space, beginning with the earliest, is:
first humans in space, first humans on the moon, first space shuttle flight
This timeline includes:
- First humans in space - Yuri Gagarin in 1961.
- First humans on the moon - Apollo 11 mission in 1969.
- First space shuttle flight - STS-1 in 1981.
So the correct response is:
first humans in space, first space shuttle flights, first humans on the moon