The correct order for the key events regarding the exploration of space, beginning with the earliest, is:
first humans in space, first space shuttle flights, first humans on the moon.
This is because:
- First humans in space - Yuri Gagarin orbited Earth on April 12, 1961.
- First space shuttle flights - The first Space Shuttle, Columbia, flew on April 12, 1981.
- First humans on the moon - Apollo 11 landed on the moon on July 20, 1969.
(Note: The order I provided is corrected based on actual timelines. The options given seem conflicting on the actual historic events. If we strictly go by the options you provided without correcting them, the second option is the one that follows the correct sequence considering the listed events.)