Arrange the following events in space exploration in chronilogical order

1. Sputnik I was launched into space.

2. Explorer I was launched.

3. Humans orbited Earth.

4. The first human stepped onto the moon.

i believe the correct answer is option b. most eastern european nations joined nato.

though i could be wrong, option d. the eastern european nations were granted complete independence, would be another choice.

hope this ! : )

he was able to speed up production of the processing of seeds