If the earth's relationship to the sun were any different, life on earth may not have been possible.
a. true
b. false

Yes, this is true.

Life needs some conditions, such as :

-it can't be too cold: many life processes can only happen in a certain temperatures and if it's too cold, they won't happen.
-it  can't be too warm either: life also doesn't thrive in too high temperatures.

This means that the planet needs to be in a certain distance from the Sun to develop life - the statement is correct